Using a 7950X3D with windows 11 and this game just won't start, I've tried compatibility mode and I disabled my internet but nothing works

I'm in the same boat with the same CPU. Thought GOG would make it work but it totally crashes. Steam at least got into the video starting up and playing.

I do see Process Lasso log

C:\Windows\SysWOW64\WerFault.exe after Assassinscreed_dx10.exe launches. This happens after assassinscreed_game.exe launches.

Looking in event viewer,
Exception code: 0xc0000005
Fault offset: 0x00010c74
Faulting application name: AssassinsCreed_Dx10.exe, version: 1.0.2.1, time stamp: 0x48067113
Faulting module name: AssassinsCreed_Dx10.exe, version: 1.0.2.1, time stamp: 0x48067113

OK figured it out using parts of this post:
https://steamcommunity.com/app/15100/discussions/0/846946588489661882/?ctp=2#c4334097152430411557

They suggest using Rynen Master Tool to put the processor into "Game Profile" mode where the upper CCD is disabled. I think that's heavy handed and not necessary.

With Process Lasso, use set CPU affiniity on the process before it crashes to assign cores 0,2,4,6,8,10,12,14. Those are all the real cores of the first CCD (not the hyper threaded ones).

After making this change, I launched the game. It crashed once, so I tried once more and it took, and played. No issues through the first level. Hope that helps you.