It is kind of weird thay it hasn't been done yet, but in that thread they posted it sounded like it's totally possible at the moment.

As I mentioned above, I don't feel strongly about Bluesky winning, I just don't like misinformation. (I also have other things I care about more that take up what little free time I have for tech stuff already, so I'm not going to undertake something major just to prove a point.) If there's really a fundamental problem with AT Proto and how it can be used, Doctorow's post should have made that explicit.

I did find a (more recent) post that goes into detail about what's lacking, and I've edited my original post accordingly.

the reason there arent relays is that theyre expensive to run (150$+ a month, if you rent, and the cost seems to scale linearily with the amount of users on the network), i saw a blog about someone who hosted one briefly (https://whtwnd.com/bnewbold.net/entries/Notes%20on%20Running%20a%20Full-Network%20atproto%20Relay%20(July%202024), and it isnt even that hard to setup, it's mostly just the cost.

Also, relay's aren't technically needed, you could make an appview that pulls from pds's directly.