Disclaimer: This review was made with regard to Superhuman ironman difficulty. I bet Beginner is really chill and fun.
Some sort of breaching / peeking mechanic is desperately needed. As it stands the only way to turn a corner is to eat a face full of reaction fire. This is particularly bad inside UFOs and in residential parts of Terror missions. Grenades are too awkward to use in these situations because it requires a whole turn of TUs to be able to prime and throw one and usually opening the door is a death sentence.
I've never seen a game so reliant on RNG. You'll miss your shots most (80%) of the time, and aliens will frequently be able to survive multiple hits (and never miss), so volume of fire is necessary - your infantry are so bad, cheap, and disposable (you are barely punished points-wise for casualties) that the only viable option is to mass as many of them as possible and charge. You have to research to unlock usable weapons, and towards the end of the first month you should have laser pistols and halfway through the second laser rifles. These are a great improvement but you won't be getting any body armor until towards the third month, so infantry spam is still the only working strategy. I'm not sure the starting rifles even penetrate the armor of cyberdiscs or reapers, so you don't really have choice in tech path here or you'll automatically lose your first terror mission.
Oh, yeah, and alien psychic powers are ridiculous in terror missions and there is no way to play around them. They don't require LOS and you'll encounter them extremely early in the game. Good thing you brought so many expendable troops! Feel free to execute the mind controlled agent.
So, not so much in the way of strategy here, but this game is older than I am so it's understandable. You have no control over the outcome of the game, you can place your soldiers in the most advantageous positions possible but if the RNG disagrees you will always lose.