I’m not up to date on the recent changes, but problems we had with vacuum were more computation and iops related than memory related.

Basically in a database with a lot of creation/deletion, database activity can outrun the vacuum, leading to out of storage errors, lock contention, etc

In order to keep throughput up, we had to throttle things manually on the input side, to allow vacuum to complete. Otherwise throughput would eventually drop to zero.

No, vacuum issues are not solved. This will reduce the amount of scanning needed in many cases when vacuuming indexes. It will mean more efficient vacuum and quicker vacuums which will help in a lot of cases.

There was a big project to re-architect the low level storage system to something that isn't dependent on vacuuming, called zheap. Unfortunately it seems to have stalled and nobody seems to be working on it anymore? I keep scanning the release notes for each new pgsql version, but no dice.