EdgeDB is designed on the assumption that it fully controls and manages the underlying Postgres instance. This is why we can have a better/faster binary protocol, proper connection pooling on both client and server, and many many other perks. Making it an extension would drastically limit what you can do with it, and besides, it will take years to make this extension available on AWS and others anyways. All in all, it's not worth it, even though on a surface it sounds like a good idea.
