You aren't writing this for public opinions, presumably.
I've also written a Postgres wire protocol implementation and a blog post on how to do so, which people are welcome to say "It's terrible" about if they wish.
The fact that you've also dabbled in this area could lead to a far more interesting discussion. Wouldn't mind seeing your blog post. Who knows, maybe I've already read it at some point?
btw the reason for extending eg Array is to make for a much better surface API when using the library.
Being able to do const [user] = await sql`...` leads to some very readable concise code.