For some reason whenever I try to play, everything goes fine until I get to the loading screen after the main menu. It loads the game almost to 100%, but then the game freezes and crashes. I've tried reopening the game, reinstalling it, nothing works. I haven't changed anything in the files, the only thing I meddled with that I can think of is organising my CC folders inside Packages, which is supposed to work considering I have the right version and the cfg file says I can do it.
The game had been running perfectly fine on my computer for two years now, even with all of the CC I've downloaded, and I haven't downloaded anything new before it started crashing. This just happened out of no where. What can I do?

Just to narrow the issue down a little, typically one would pull the TS3 user game folder out of Documents to the Desktop (or renaming it), thus forcing the game to spawn a new one on its next attempted launch. If you can get a new game started up on the clean folder with no content an no prior saves, at least you will know that it's something to do with your current game folder and not the install or some other kind of breakage.

If you happen to be using NRaas mods, by the way, the MC Progression add-on module will crash the game on startup every time if both the MC and SP base mods are not present. The NRaas Cupcake mod will crash the game if the bakery store set is not present or has suddenly gone missing on you. I wish there were gentler ways for these two to fail, but in the meantime these two conditions do tend to trip up some users.

Echoing the other posts, if it's a crash at the startup loading screen, it'll probably be dodgy CC (try to think of what you've added recently and if you play TS2 or TS4, make sure you don't have any of that CC in your folder. If it's upon loading your save, then it sounds like you have a broken save.

Oh sorry, I might have been a bit hasty up there. Wasn't focusing on the possibility that the saved game to be loaded might have already been selected, I thought the player wasn't getting that far in the process yet.

Yeah, didn't figure out it might be the issue only up until a few minutes ago. Still weird, considering I haven't done anything out of the way with that save, but oh well, I'll try another save and see how it goes!