So, while my PC isn't all powerful for The Sims 3 with all 20 of it's expansions installed, but the gameplay itself plays very well, especially on smaller worlds. However, besides normal gameplay, some other tasks, such as saving, going back to Edit Town after editing a lot, saving to library, loading a world and stuff are much more problematic.

What I mean by that, is that whenever I want to go back to Edit Town after editing a lot for example, it'll just hang on the "Loading" screen with the spinning plumbob. Loading worlds and the game itself also take MUCH longer than they used to, the world loading often hang on 99%, especially sub-neighborhoods, saving can either take a very long time, or just hang for eternity. What on earth is causing these problems? The fact that it's running on an HDD instead of my teeny-tiny 120GB SSD which is already almost filled up with Windows crap, the fact that it has a lot of expansions to load, or what?

To be clear: I have few custom content and gameplay script mods installed, and a few CAS items. Maybe I should try starting the game without ANY of those installed. My PC's specs are:
AMD A10-7890K 4.10 GHz 4 cores + 8 threads
Nvidia GTX 1050 Ti 4GB Gigabyte
8GB DDR3 RAM
120GB SSD for the system (but NOT the game )
1TB HDD for games, VMs, downloads and stuff (This is where the game is located )

Note: CAW's Edit In Game also seems to have these exact same problems, but that's par for the course in my opinion. Also, I know exactly that the game is horrendously programmed, so I shouldn't blame my PC for this, but you get my drift, I hope. Plus, I don't want to hear any "your PC is far too weak for TS3" and stuff, unless that's the true reason for all of this to happen. In that case, please kindly explain exactly what's wrong.

Don't forget Overwatch. Overwatch, Error Trap, and Kuree's Save Cleaner if you've been playing your saves for longer.