The solution is to lean into what Lemmy (and the Fediverse) was designed to do - be decentralized.
If we have more instances running, it would lighten the load on the larger instances (smaller instances can still subscribe to the larger one's communities and such).
I think ads isnt a great idea. Firstly, generic ads don't pay much, for actual good income you need to target ads, which now digs into users privacy and from there we have a slippery slope.