Middleware solves this, but that also would run contrary to what @fiatjaf feels clients should be...

Imagine if your email client reached out to every mail server that you wanted to receive emails from... it would be unusable. This is Nostr today, and so everyone uses a few relays to minimize connections.

(in reality email has become this too due to anti-spam rules, now the overwhelming majority of email comes from big cloud)

A middleware would act like a email server does today, its always online receiving messages for bulk users, indexing, and serving them to your client efficiently. It would be no more centralized than email, but still better due to Nostr using signing/encryption natively that could better resist centralizing forces.

Primal is the only Nostr client I'm aware of that's doing something like this, and therefore most usable. I hope to eventually get around to making something more generalized to integrate Nostr closer into our apps.