Disclaimer: Supabase is a great platform, with by far the largest ecosystem and community.

However, if you're looking to leave, the reasons usually come down to three things:

The pricing gets non-linear at the exact moment a project starts working

PostgREST doesn't scale gracefully to complex relational frontends

You have requirements (self-hosting mandates, a reactive data model, compliance regimes, or AI agent workflows) that the platform doesn't model well