If you've recently tested your mods and custom content to make sure they're up to date with the latest game patch - August 16 2018.
https://help.ea.com/en-us/help/the-sims/the-sims-4/the-sims-4-updates/
You may need to clear your game cache and delete the localthumbcache.package from the Sims 4 folder to help with troubleshooting.
How to Delete Cache Files
https://sims4.crinrict.com/en/2014/09/delete-cache-files/
Custom content can become outdated with most new game patches. If the game works when the Mods folder is removed, then one or more of the mods and/or custom content has become outdated and will need to be removed or replaced. EA/Maxis aren't responsible for broken mods/cc. It's up to the creators to fix.
Disabling or turning off both mod/cc options isn't enough of a test.
Try the 50/50 method:
1. Move all the mods and cc out into a temporary folder on the desktop.
2. Move a few files back at a time. Load the game to make sure it loads and everything is good.
3. Delete the localthumbcache.package from the Sims 4 folder.
4. Repeat steps 1 - 3 till there is no more files to check.
** While your testing, don't save the game. If you find any problems, delete the mod or custom content file.
How To Find Problem Mods and CC
http://simswiki.info/wiki.php?title=Game_Help:TS4_Finding_Problem_Custom_Content
