There's no game that can scratch the itch of a space sandbox the way X4 does. Despite all the combat jank and having to fight against the terrible UI to get things done, I can't stop myself from loving and recommanding this game.

I'll start with the main positive : the scope of the game is incredible. The fully simulated wares/resources economy and logistics is the backbone of the whole sandbox, and will give you the opportunity to rise as a trader, a miner and/or a fighter. The usual flow of the game makes you start from humble begining by piloting a single small ship, to eventually rise after a lot of time and grind to the owner of massive autonomous network of ships covering these three aspects.
The "endgame" will mix these aspects with stations building, becoming your own economic powerhouse by producing wares that you can sell or use to feed your own shipyards to produce ships. Threats like piracy, relentless Xenon incursions and potentially other factions you may have angered will also make you rise as a military powerhouse, having several strike groups with specialized compositions to adress those threats.

The whole military side has great things going on, you can build your own carrier strike groups with a fleet carrier as a command ship and capital ships/frigates/small crafts/supply ships having specific orders around that carrier. Each ship you order to build can be customized with the weapons, shields and engines you want to specialize them. Every ship has an interior you can walk around, with bigger ships having large command bridges filled with your crew, great for immersion.
The strength of X4 is you can play and immerse yourself on any component of the fleet you've designed: The admiral walking in the main bridge of the carrier giving orders, the captain of one of the escort destroyer engaging an enemy capital ship, the pilot of one of the interceptor scrambling from the carrier to intercept incoming bandits. But there's also some criticisms to be made there, which i'll adress later.

The game has 6 main races to interact with, divided between subfactions. Some of these divisions are open civil wars, some are peaceful but fragile status quos. This is where the main quests/missions come into play. They will make you fly and walk around to acquaint yourself with the various factions and cultures, and will end up with you being the decisive factor to their future. You can choose to be a space UN diplomat and ultimately fix every conflicts, or think about your profits by picking the warmongering option, creating more wars so more demands for weapons, ships and wares to build them. Or any mix of decisions that will fit to your roleplay rules, this is a sandbox after all.

I'll now talk about one of my experiences that I hope will highlight the best side of this game. As a long time Terran enjoyer (best faction in X3:AP by far, and beautiful ships all around), my main motivation was to roleplay as a Terran loyalist using his growing influence and power to shape the whole sector favorably to secure the future of Earth. The Terrans can be described as active isolationnists focused on fighting the Xenon threat by any means necessary, their methods giving them a terrible diplomatic standing with most factions.
My goals led me to undermine the Argon Federation as they're the biggest threat to Terrans, completely boxing them from interacting with the rest of the galaxy. The Argons in this playthrough managed to secure decisive victories against the Xenon, the Holy Order and the Zyarch Dominion, snowballing them into a superpower. So my plan to curb them led me to secure my standing with Zyarch and use the entire might of my carrier strike groups to secure their territories against the Xenon who wiped 3 of their sectors. Once the Xenons were kept at bay, I started to fix Zyarch's struggling economy by continuously filling their wares shortages with my freighters, and eventually securing contracts to build them new defense stations.
After a lot of time, Zyarch managed to build back a strong military and take back all the territory lost after a few decisive victories against Argon incursions. I was so happy to see how I influenced a whole war outcome to my favor without firing a single salvo. The whole operation was aslo very profitable as Zyarch was willing to pay a lot more for wares because of the shortages.

Now the bad part. First the UI is a hard wall that fill filter a lot of player, very understandably so. It will take anyone playing this game a lot of effort and searching to familiarize themselves with the various menus to make something out of this game.
Even when you get to the point of understanding most of it, it won't get any more confortable to use them. I'll give an exemple there: If you want to rotate out your fighter pilots from the carrier to train a new batch of pilots (which is the only serious way to train new captains), you will have to switch each one individually. That means selecting the fighter you want to change the pilot, pressing "c" to communicate, select 2 dialogue options to reassign him elsewhere, go to your crew menu, select the crew you want to promote and assign him to that ship. Great, it's done! Now imagine when your proud Tokyo-class fleet carrier hosts more than 50 small crafts and you want to rotate everyone... fun times indeed.

The second bad point is the jankiness around combat. While the combat is good at every level as mentioned previously, it won't be as good in each aspect as a space game specialized on combat. It will be hard to explain with words, so watch a few videos to judge for youself (Captain Collins on youtube is a good reference). For me it does the job well enough considering the scope of the game and the fact you can operate a whole carrier strike group to begin with, which is very rare for a video game.
The REAL jank comes from the unavoidable frustration you will experience with the AIs of your ships. You WILL experience again and again your anti-cap destroyers with elite captains rush under a Xenon K and get destroyed instead of using its superior range to engage it safely. You WILL see your fighters slam on your carrier when coming back after a sortie. You WILL lose bombers due to them not attempting to dodge enemy fire at all.
If you have a mindset of not reloading saves and live with the consequences instead, it will be an infuriating experience.

Another minor criticism i'll give about combat is the general lack of capital ships compared to X3. Only one faction has an escort carrier, most factions lack an XL battleship. There's a gap between M frigates and L "destroyers" in every faction (the current destroyers we have are definitely cruisers based on modern Navy roles, and we're lacking ships that would fit as proper screening destroyers). There's a lot of mods hanging around to fill these gaps, but I would love Egosoft to adress this at some point. I'll even forgive them for not bringing back my beloved X3AP Kyoto-class Battlecarrier if they fill the ship roster gaps.

Finally, a brief summary of the points i've not talked about:
- The graphics are okay, not stellar (heh) but does the job well considering the scope of the game and Egosoft's available resources
- The music is great, "Rise of the Protectorate" is now one of my favorite video game tracks
- The performance can dip a lot with big stations or when lots of ships are involved. Considering the scope of the game again with how big battles can be and how busy sectors can be, this is acceptable but more optimizations would be welcomed.
- The sound design in general is uneven, good sounding weapons and ship engines, bad voice acting and overall arguable sound mixing
- The vanilla "grind" is real, expect to throw dozens of hours of repeating the same actions before reaching the point of getting a carrier strike group or a proper tycoon empire going on
- Lots of mods going around to customize your game the way you want

So, X4 recently did an update for cloud saves, which undid 2 years of progress for me... It's made me introspective, and I realize I'm in the unenviable position of having to earn that all back or give up.

I give up. And not just because I have to do the Timelines DLC all over again.

I have always said that Egosoft is a company of incredibly talented programmers who have never made a game before. These guys can make a interesting mechanic or cool-looking model, but they seem allergic to functional game-design.

In short, the game equates time spent with difficulty/challenge. That tends to be the case with open worlds that encourage you to "write your own story".

The only difficulty is learning the controls/systems. After that, it's just mostly waiting for stuff to happen, with the only thing breaking up the monotony being repeatable side quests or the occasional, poorly written, story quest. You're just ALWAYS WAITING for the thing you really want to do to happen. There's really no challenge.

You'll notice I have a lot of rare achievements on this game. That's not because they're hard to get. It's because everybody else isn't a dumbass. They play on creative or with mods and don't earn achievements.

Lastly (and this might not make sense if you haven't played the game) the universe isn't really "yours." The devs go out of their way to prevent you from having an identity in the universe or break cannon (unless you just blow everything up). You can't even look different from the other factions. You can't reverse-engineer any rare ship you find and have an unique armada, and ship skins have a limited amount of uses. Your crew will always be of another faction. You can't have equipment unique to your faction. You will always be "another-faction-but-Walmart-version."

EVE Online + Stellaris + No Mans Sky. I find all DLC to be good value and would purchase more. I would purchase X5. This is the most i've ever played a game before it felt "solved" and done. 218 hrs as of writing.