[perrygeo]

uuids as a primary key can be a major insert performance bottleneck since they are randomly distributed.

data isn't indexed so queries other than select-by-uuid will be slow (unless you're putting indexes on special keys which is just an ad-hoc schema with extra steps)

data migrations will be painful and require full table scan/rewrite (hope you can afford downtime)

No relationship between any of your data; it's all just independent blobs of data that may or may not be related. No referential integrity means you need another out-of-band process to make sure everything is pointing to valid data.

I get the temptation to nope out of schemas and do schema-on-read. Worked for Mongo, right? (did it?) However, postgres allows an even better option: create an actual schema for your business domain THEN add a jsonb column to every table. If you need to add extra stuff, you can just shove it into the data column. You get all the benefits of a static schema plus an option to jump ship and do JSON in a pinch.