Help with screen tearing/FPS on old Mac

Hi, I play on a 2011 MBP and performance has never been good, but lately it has become virtually unplayable with massive continuous screen tearing while unresponsive to input. Feels like 1 frame every 1 or 2 seconds sometimes. Almost every arena game at some point, and 15-25fps otherwise.

I would really appreciate any help with this problem, as I'm sure would anyone else in the same boat now or later. What can Mac users do to improve performance?

I've already put all video settings on minimum.