alt Hacker Newsjournald is IMO the worst part of the systemd ecosystem. You're better off using it only as a router and not storing any logs in it. The indexing system it uses is slow and provides no control over chatty subsystems - you cannot truncate the logs for just a single identifier. For all the use indexing is doing you will get better performance out of a modern grep like ag or rg. Structure is worth something but it's better off somewhere other than journald.
I recently put a lot of effort into reducing logging because of excessive writes. It was so much easier when everything had its own log and you could just look at which files were growing.