Since all you sims have gone missing from all saves then you have something going on that is certainly not right. I thought it might be mods but you say you never used them.
Have you tried creating a new game? If you have and still have the problem, there are a couple of things you can do.
First, try a game repair.
The second thing you can do is a folder reset. Just rename your "The Sims 4" folder to something else or move it somewhere else then start a new game. If the problem is gone, then save and exit. Then copy your saves and tray folders from the old folder to the new one and try again. If you use any configoverride like a custom graphicsrules.sgr file, or custom music, copy those folders too. Then start the game.
Hope this helps.
I’m afraid of creating a new game and losing everything forever ☹️ I did try a game repair as well as deleting my localthumbcache. I can definitely try resetting the folder thank you for the advice!
