any tips howto play mgs5 after not playing for 9 years?

[Blitz4]

9 years is a long time. i just awoke from a coma. to find out that, mgs5 is weird.

so beginning of the 1st mission. i'm told the guy won't make it 3 days. ok. i'm given several hidden objectives that arent told what they are or why i should care. i found a diamond that was a hidden side mission. cool. unsure what the reward is. maybe i should keep looking for diamonds. after a while what i collect goes back to base. cool. no mention of what the resources i'm collecting are for. if i should go faster or slower. it's like the open world aspect of the game is conflicting. one i want to 100% the objectives given to me, they are question marks so i have to spend time to uncover them. two is the primary objective will die in 3 days and after 1 day i'm warned i need to move faster. but the faster i move the less i get to loot. it's like the open world aspect is holding mgs5 back as it's not fully fleshed out. why hide the objectives? why hide the rewards? why punish me for being slow because I want to collect more for what I know is upcoming the motherbase? i'm conflicted with what todo. on one hand there's a speedrun on the other there's a supply motherbase, i imagine the line i should walk lies somewhere in the middle.

i also remember the reason i stopped playing was because of all the free stuff they gave me for motherbase. i fixed that by playing offline. but i'm not sure how i'm supposed to play.

i don't know if i should spoil mgs5 in some way to progress to tell me what the side missions are, or do what i'm told and stop looking for side missions or if collecting stuff even matters.

EDIT:
any advice or maybe a mod you'd recommend that i should use that'd flesh out the rough edges of the game for me?

[Rastrelly]

All the "free stuff" is eaten by insane prices of high-tier gear. None of which you need because every mission is beatable with tier 1 stuff.
All the "hidden objectives" are there to have fun playing. They get unhidden later.
All the side ops are optional except those that are not (and those that are not are very explicit about that).
Most mods out there expect you to be quite familiar with the base game which is huge already.
So just play the game.

[MrSteel300]

just start killing people in free roam, nothing you do there matters except you know resources but they are easy to come by, go full lethal and kill bases over and over to get used to the movement

[MrSteel300]

send your soldiers to combat deployment for gmp

[Watereaters]

Also some of the objectives can’t be completed on the first mission completion since you lack the right tech for them.

[Original Cast Recording]

Speedrunning the whole game is one thing. Speedrunning individual missions is just a matter of what you feel like doing at the moment. You get a bonus points for faster completion. You also get a bonus for no alerts.

If you want materials, you can get them in free roam. By the time I got to the point where I just running around having fun, I was never short of materials.

There isn't much you really need the best gear for if you're not doing FOBs.