The game can't/doesn't want to write cache

@bi0hzrd  I would find it fascinating if using DSR was what fixed the icons, so please test that and DEP separately and let me know what you find.  (DEP shouldn't be necessary anyway, but now I'm curious.)

For the world loading times, it's pretty clear that the WorldCache folder is the issue, but not why the game isn't reading it.  I'd suggest testing without DXVK just to make sure this isn't a side effect of that utility—it's very new, at least in terms of wider use, and any problems with it aren't well-documented yet.  Deleting the files and repairing the game is enough to revert the changes, although that would revert your .sgr files as well as anything else in the program files, so make backups if you don't want to redo any edits you've applied.

If you've made other edits too, please skip them for at least one round of testing.  That applies to any .sgr edits not directly related to getting your GPU recognized as well.  I realize that it's kind of a hassle to set everything up just the way you like it, but this is such an odd error, with no known cause I can find that we haven't already covered, it's time to eliminate as many variables as possible.

I'd also suggest trying to play with your computer completely offline.  And just for fun, see how much this mod decreases a new save's initial loading time (Sims Asylum, so you'd need to sign in to download it):

https://simsasylum.com/tfm/index.php?/topic/497-no-auto-placement-of-community-lots-in-ea-worlds-requires-at-least-one-of-these-eps-ambitions-showtime-supernatural-or-seasons

Some of that first loading time is directly related to placing these lots, although not all of it.  So I'd like to know how much of the problem is this and how much is the WorldCache data not being read.

@bi0hzrd  I read through this thread and the one at NRaas again in case I missed anything, and I have a couple questions and suggestions that might feel redundant to you, but I want to make absolutely sure I'm not overlooking any possible sources of error.  So please bear with me.

As I mentioned before, a lot of the longer loading time for a new save is due to the game trying to place the EP lots in the world.  (Part is probably creating WorldCache data, but I'm not sure how much.)  As you can imagine, this takes some calculating.  I don't know why the game would be calculating this again in an existing save; that's not standard behavior and I've never seen it do so myself, at least as far as I can remember.  But the fundamental problem very much seems to be a failure to read certain files, so not reading whatever data says "this process has already happened" is in line with everything else.

This reasoning of course only applies to existing saves, not new ones.  The default behavior is that a new save should take extra time to load regardless of whether you've previously loaded that same world, again due to placing those EP lots.  If you're seeing brand-new saves take the minimum amount of time to load, but only within a few hours of the last time you loaded that world, that's the oddity, although to be honest I haven't tested this myself.  So I can't say that this is unique to you rather than a random glitch built into the game.  I will test myself a little later.

A couple suggestions though:  First, you can try running Sims 3 as an admin, as in, right-click the executable or its shortcut and select "Run as administrator."  (Having an admin account allows this function but doesn't apply it by default.)  Please also make sure that Windows Defender's Controlled Folder Access hasn't reenabled itself.  Here's a guide in case it helps:

https://crinrict.com/blog/2019/03/windows-10-defender-controlled-folder-access.html

Please also let me know if you've moved the location of Documents, or created a symbolic link to redirect the Sims 3 user folder.  Essentially, I'd like to know if the user folder is stored anywhere other than the default C:\Users\your username\Documents\Electronic Arts.  And what kind of install do you currently have?  I know you tried a few, all with the same problems; this is just in case I need to reference something platform-specific.

Your GPU can definitely handle the increased load of setting DSR to 1.78, i.e. rendering Sims 3 at 1440p, so there's no reason not to keep doing that if you're satisfied with the results.

@puzzlezaddictI always run the game as an administrator, so that part is fine. I will check if Windows Defender is blocking access to the folder and will write later about what I find out.

Yes, my Documents folder is located on drive D instead of drive C, BUT I also tested the game by installing it on drive C (with the Documents folder also on drive C), but unfortunately, this didn’t yield any results. Currently, I have the Steam version installed.

@puzzlezaddictI followed the guide exactly as instructed. After that, I entered the game, saved it by choosing a random family, and then logged back in after 2 hours. Yes, the game loaded again as if I was launching it for the first time.
I noticed something else: it seems that the problem is not only with WorldCaches but also with the fact that my game stops reading the Mods folder after some time. That's why the mod you recommended above didn't work for me during the first test. So, the game sees the mods because they work in the game itself, but apparently, some of them stop working after re-entering the game after some time. For example, I chose Bridgeport, and it loaded again for 2-3 minutes, with the loading stopping right at the end. This means the mod isn’t working, even though I haven’t touched or deleted it at all. I closed the game through Task Manager and re-entered it, after deleting the town cache that had been created, and the town loaded in just a few seconds. This time, the mod was working, and the loading bar didn’t stop at the end. Very strange things are happening with my game.

@bi0hzrd  I don't think there's a good reason to reinstall Windows right now by itself.  The only times I suggest it are when a system appears broken on a fundamental level, for example when basic repair commands throw errors that can't be addressed; or when the user is so tired of testing, or the testing is getting so time-consuming, that it would be simpler to reinstall Windows; or when it's a new computer and there isn't a lot of data to replace or reinstall.

If you're at the point where reinstalling Windows is easier than troubleshooting anymore, that's reasonable.  But it's entirely your call and somewhat subjective.  The other part of this is that aside from suggesting you try another new Windows account, now that you've made other changes, I'm out of ideas, and it sounds like you might be too.

Still, I'd suggest a repair install before entirely wiping the system:

https://www.tenforums.com/tutorials/16397-repair-install-windows-10-place-upgrade.html

It doesn't take that much time and shouldn't delete your data, although if you get to step 13 and are not prompted to keep personal files and apps, back out and start over.