Updating Unity Caused Severe Drop in FPS

I've tried that. I severely doubt it has anything to do with my code or how I've setup my objects. I added literally two things before building it again after the update. I took those out and it's still super laggy and choppy despite the fact that it was fine before. I've spent like a week and half just going through my game and optimising absolutely everything(compressing audio, making gameobjects static, reducing collision boxes and rigidbodies e.t.c) but it's made no noticeable change whatsoever. I was getting 30-60 FPS. I downloaded Unity Hub and updated Unity and now I'm getting 15 FPS at best despite little to no changes.

Yeah. It's not very good admittedly, but I didn't have any problems with FPS before the update because it was a pretty simple game.