It will be stopped with bitcoin lightning. For example, if somebody wants to reply to your, they have to pay sats that is configured by you.

Can't stop bots , adding some kind of cost to creating a private key destroys the permissionless nature of it and creates a barrier. While at the same time making someone, somewhere in charge of what this barrier is, should be.

Paid relays. Put your attention behind a Bitcoin paywall, go to https://relay.exchange for a list of services

self-moderation and perhaps eventually a consensus mechanism on the protocol level. As in X users on note Y blocked / flagged account Z. This gets relayed across the network for other relays (users) to verify and forming a consensus banning the content, bots or whatever.

But for now I'd say self-moderation and selection of good relays. I don't get much spam but I also don't use many relays.