@MysticMaoDon't try putting old mods folder and old saves folder into this new folder! I understand that without it the game is working.
Check if you still have this problem in the newly created game folder without old saves and mods folder. Start a new game with the random sim and play for 10 minutes. Save and quit.
If the problem disappeared
Delete in the new game folder following folders:
"saves" and Tray.
Go to "The Sims 4 old" folder and copy - your "saves " folder. Paste this folder in a newly created game folder.
Do the same with Tray folder and TrayDeleteItems file
Check if the game is working now with old saves.
If all is OK check if there are newly updated version mods you are using.
Then copy and paste your mods and CC from old mods folder to the new one. First copy the scripts mods every time checking if the game is working properly. If you have a lot of CC try 50/50 method ( divide your CC into smaller batches for example 50 pieces in one subfolder and check these subfolders one by one)
If all is OK - delete The Sims4 old folder. Now you will have only one game folder working properly.
I don't work for EA