Every captcha is a paywall. You pay 5 sats maybe less to prove you're "probably" not a bot. It doesn't remove bots 100% but it does mitigate them.

Stacker News is already doing this, in a way the issue is the broader culture doesn't know this capability exists.

In my opinion it needs to be built out and matured, the primary challenge is the speculation and misinformation IMO which confused the public about what bitcoin is - to the point that lightning is never mentioned and it should be.