Couple of points here: https://medium.com/geekculture/appwrite-frequently-asked-que...

Both products are great, at Appwrite we created the majority of the product from scratch in aim to have tailored made dev-experience which was a big reason for starting the project from the first place.

Supabase uses Postgres instead of a Firestore like database, so it's not really a clone of Firebase.

Postgres supports jsonb which I've used with Supabase to act as a Firebase analog. I just pushed all data into a JSON blob rather than setting up tables, it worked well, pretty much the same as how I used Firebase.

I'm trying to be as objective as I can, but building the entire ecosystem around a single product like Postgres ( even though tried and tested ) comes with its own downsides...