Lemmy.world just finished pushing significant stability and performance improvements to the Lemmy codebase and to their own server, and from what I’ve heard it’s lead to significant improvements. I agree that Lemmy is unstable, but it’s also beta software undergoing rapid improvement, and I’m optimistic on where it will be by the end of the year.
I feel like most of the problem would be physical hardware. Costly servers that would need to be able to meet Lemmy’s growing demands.
I’m not sure how much optimization from the software side can be done to reduce resource requirements. There’s certainly things that can be done to improve user experience though.