Game failed to load

YeonnamdongV​  From what you just described, the source of the problem is obvious unless you haven't mentioned everything.  It's something in your CC or non-script mods!!  So, you need to go through all of it.  So, a couple of things to try.  Make sure you haven't downloaded any Sims 3 CC.  That will usually case Sims 4 to not load.  Then go through your CC using the 50/50 method or whatever you do to find bad CC files.  You should also test all your non-script mods individually as well.

About your CC:  This will be really time consuming if you have a lot of CC, but it is worth it in the end imo.  Get Sims 4 Studio (S4S).  Look at every CC item you have.  If it doesn't show up in the S4S 3D view window and is NOT a default replacement (default replacements do not show in S4S), then the file is probably broken and should be removed.  Then look at those files again in CAS just to make sure they do not show up in the game.  I suspect you will find what I did when I went through mine.  I found well over a 100 broken files that had been in my mods folder for a long time.  Some for years.  And they had never worked but I never caught it.  Once I cleaned out all those files, it made a real difference in how my game loaded, and how CAS displayed things.  Both were a lot faster.  I also found a large number of things that weren't tagged properly and didn't show in any of the CAS clothing categories, only when you looked at all CAS items. So, fixing those made them show up correctly.

Hope this helps.

YeonnamdongV​ The currently available version of a mod can still be broken. There's a LOT of broken mods available to download. Start at Previously Broken mods and CC and the current Broken and Updated Mods and CC list. Delete EVERYTHING listed on those as broken or obsolete. Then try again.

If you still have issues, it's time for  50-50 testing of your mods folder, as you may have a broken mod or CC item that cannot be reported on the forums or that hasn't yet been identified.