Supabase developer here. I came from Firestore to Supabase due to running into a lot of limitations you're seeing. Just my biased opinion, but looking at "newer/more modern DBs" is not necessarily the route you want to take. That's why I looked at Firestore and ended up at Supabase. PostgreSQL is not "newer/more modern" but it's time-tested, battle-tested, and I know thousands of companies have used it in production for decades. I prefer to go with something I know works, will work at scale, and has tons of community and commercial support. FWIW