What exactly do you mean by this? Did you report it on Github?

The Lemmy backend causes the Postgres database to use more and more RAM, to the point that it crashes with out of memory issues randomly and causes other processes to go down with it. I have reported the issue multiple times and I am not the only one with the problem since many years, but apparently you think this is a Postgres misconfiguration issue. I tried a lot of settings regarding the Postgres config but it doesn't change much. Different versions of Lemmy had this issue to different levels of severity though, with the newest version being quite bad again after some improvements in earlier versions. I think other instances have largely given up on fixing this as well and just regularly restart the Lemmy backend, which resets the RAM use of the database.

To be clear it uses the lemmy.ml api to get a list of most active communities. Most of these communities are not hosted on lemmy.ml, and the data looks almost identical to that from lemmyverse.net (more details).

The idea of a centralized source of popular communities is generally bad and if you want a way to have better discoverability the source of it should be left up to instance admins to decide. I agree that lemmyverse.net also wouldn't be a good choice for that, and admitably I am not happy about Piedfed using that for similar purposes, but at least it is much easier to modify that behavior in the Piefed.