I agree that the bot accounts are annoying and getting worse, but I don't think that making it more difficult to create an account is a good solution here.
Yet, it's possible to create a new account and get un-shadow-banned after a few hours. Dunno if this speaks volumes about how great HN's mods are or if it just means that other forums a really lacking in moderation for one reason or another (like "we have shitposts but it drives up engagement").
The trouble is that HN is centralized, like most forums. So what if it stops working the way it does now? There are likely many forums like HN with good algorithms and mods, but we won't all move to the same one, we'll scatter around. There isn't even a competing HN; lobsters is for narrower subjects, reddit is trash, what else is there?
HN is also different from Reddit/Digg because it only allows text and links, but this is the same as Usenet and most old-school forums. And then there are some intangible cultural differences, but every platform thinks that they're special, so there's nothing really unique here.