NIP17 makes relays easily spammable. How is that a good solution? At the minimum you must accept and decrypt all DMs from anyone. We know only one good (read: not super centralized) solution to the spam problem: payments. So if you get people to pay for DMs, problem solved. But you won't probably, not in a social media context where everyone assumes free is the default. Nostr has not "botched DMs" because we always knew the solution, we botched the business model, because shitposting doesn’t pay for DMs.