The problem is that the narrative has been poisoned by Cloudflare and Google (for Recaptcha) - they both overstate the size of the problem, as well as the effectiveness of their solution.

In other words: when someone demands "real solutions", they're typically expecting a degree of solution that quite likely just does not exist at all, to solve a problem that isn't as severe as people believe, just because that's the bar that those companies have set in the public discourse.

This makes it impossible for well-intentioned people to 'compete' with these services, because whatever alternative is suggested (hidden form elements, a random VPS provider with DDoS mitigation, serving assets locally, etc.) is immediately dismissed as "that can't possibly be as effective / effective enough", even though it'd be perfectly adequate for the vast majority of cases.

The alternative and competitive solutions exist, and have existed for a long time. You don't need a 1:1 replacement for these services. People just often refuse to believe that the simple alternatives work, and won't even bother trying.

(For completeness, my background is that of having run several sites dealing with user-submitted content, including some very abuse-attracting ones.)