I understand that some people value their privacy above all else, but balancing this with decent anti-spam is really tricky. As someone who runs a (not large, not small) Discord guild, I personally would find it impossible to keep any public guild of any decent size running if the anti-spam were any less protective than it currently is.

It's unfortunate that this excludes some users but I think those users end up being a vocal minority. I think the benefit here (conversations without spam) outweighs the cost of privacy. And could one not just get a burner phone or something to satisfy the phone requirement?

Obviously there is a place in the world for FOSS services that preserve privacy or federate so you can manage your privacy effectively, but I think Discord eschews this for user convenience and it ends up being a tradeoff that a lot of people agree with.

(note that I will be experimenting with Matrix bridging and such in the near term future, because I too don't absolutely love Discord. But I can at least say I understand and agree with the tradeoffs and the intentions behind them.)