I use cloudflare out of my free will because there's malicious traffic out there, and I have enough control over everything.

They're only a gatekeeper because sites voluntarily enter into commercial agreements with them. There's no coercion or manipulation like Google AMP.

Customers pay for this as a feature. Why would they feel it's a fundamental problem? There's nothing that says admins need to let you crawl their site.

If people intend this to happen, sure . But how many people who put their sites behind Cloudflare is aware that this might be a side effect?

I would wager that most people that purchase Cloudflare are probably aware of the features it offers

Note the distinction. I'd wager that the vast majority of sites behind Cloudflare are not paying customers, and have not paid much attention beyond "hides my server IP slightly and stops DDOS's", without having thought more - or at all - about the wider implications.

This is exactly the case.