Sims 4 game looks very weird

ChrisSimmR  If you've enabled post processing in the graphics options, disable it and restart the game.  If that doesn't help, switch to windowed mode and restart again.

If that doesn't help either, remove your Mods folder and test.  You don't need to save your progress; just have a look around.  The next step would be to remove ReShade or anything like it, if you're using some utility that changes how the game looks.

You can also try switching to DirectX 9 or 11 mode, whichever one you're not using.  Here's how:

DirectX 11 (DX11) for The Sims 4 - A Step-by-Step Guide | EA Forums - 11811172

The codes are -dx9 and -dx11 respectively.

Let me know what you find.  If nothing helps, please provide a dxdiag.  Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop.  From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.