Really this is just fundamentally how decentralization works. This is how scaling works. This is mathematical, fundamental laws of physics sorts of things.
If you want true decentralization then it's going to be resource intensive. There is mathematically no avoiding that.
Fediverse is badly coded (IMO) but it tries to avoid these issues by not actually being decentralized. Federation means it's centralized around instances, not decentralized, but centralized around instances.
BlueSky proposes to fulfill the promise, but there is no avoiding that the promise comes with costs.