Sims 4 crashing on startup

Did you try testing without your saves?

Yep, without saves and mods.

@jaspershorns  The Sims 4 crashes in your dxdiag reference a component of the 2015 and newer VC++ runtimes, which the game uses.  So please uninstall your current versions, if you have them, and install fresh copies.  Hit Windows key-i, select Apps, scroll down to the Microsoft Visual C++ Redistributables, click on any version from 2015 or later, and select Uninstall.  Don't touch the older versions.  You can download the newest runtimes directly from Microsoft:

https://docs.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist?view=msvc-170

You'll need both the x86 and x64 versions of the 2015-2022 runtimes, but you can skip the ARM version, which is for a different class of device.  Restart your computer after installing and before trying to play.

I would also suggest running a virus scan, as your dxdiag lists a few crashes from something that looks like free software run amok.  I'm not saying you definitely have a virus, only that it's worth checking.  Download Malwarebytes (the free trial is fine) from here:

https://www.malwarebytes.com/mwb-download

Open it, look for the Custom Scan option (it keeps moving around), click Configure Scan or similar, check all the boxes both for all scan types and for your C drive, and let it do its job.  This could take anywhere from a few minutes to several hours, depending on the amount of data and whether the scan finds anything., so you may want to set it to run while you're doing something else.  Please attach its report so I can take a look.

Redownloaded VC++ 2015-22 and restarted as instructed. Still crashing.

Initial (not custom) scan found and quarantined a few PUPs. Custom scan with C: included came back totally clean. First scan attached.

@jaspershorns  The initial scan isn't as thorough as the custom one, but it can of course find some problems, and maybe all of them in your case.  The fact that the custom scan came back clean is great.

Please try playing Sims 4 in a new admin Windows account.  Make it local, as in, don't link it to your Microsoft account; you'll need to set up some security questions instead.  You'll be able to (try to) launch the game without reinstalling anything, but your saves and other user data will of course not be available, which is fine for the purpose of this test.

If the game still crashes in the new account, please post a new dxdiag.

Game seems to work fine in new admin account.

@jaspershorns  That's good news in that it means the problem is confined to your main account rather than being a more general system issue.  If you'd like to try to fix your main account, try the suggestions in the first post of this thread, specifically "Reset permissions for Documents" and "Move/restore location of Documents":

https://answers.ea.com/t5/PC/CURRENT-ISSUE-Sims-4-already-running/m-p/13276380#M264944

Documents is in the right place. Reset permissions and made sure OneDrive sync is off. Still crashing :/

@jaspershorns  If you want to keep trying to fix your main Windows account, please move Documents to a different location, at least long enough to test.

If this doesn't help, then I'm not sure what else to tell you.  Beyond what I've already suggested, addressing this type of problem is kind of looking for a needle in a haystack, and I don't really know where else to look.

Gotcha. I'll keep goofing around with things and see if I can get somewhere. I appreciate your help, thank you so much for trying!