For one thing the fact that you can't really properly use Supabase (apart from some very basic functionality) without having at least some knowledge of SQL, postgres and databases in general. IMO you'd even need fairly in-depth SQL knowledge to understand the Supabase docs and examples.
I mean to push back a bit on this -- they have a pretty intuitive GUI that they've open sourced for working with the database at a less SQL-focused level. It isn't exhaustive but for basic things like adding / editing columns, or database policies, it's pretty nice.
That's not to say there isn't room for improvement, but if you look at the github issues on all their repos, and the commits that have come out in the last few months, it's pretty clear they're pushing the way you want them to go RE simplifying the more complicated pieces down to manageable chunks.
I’m not saying it’s a bug. But I wouldn’t call it a feature either, but rather an obstacle in the way of a better/easier/faster/more enjoyable developer experience.