I don't dispute that they work well for the majority of people -- but the majority of people are not security-conscious.

However, I see people complaining about Cloudflare in lots of places other than here. The number of people adversely affected by Cloudflare is not small.

I see lots of complaints about Captchas in the “real” world, too. Not regarding the centralisation etc. aspect but more regarding how painful they are to complete correctly, but there are definitely complaints.

Regarding Cloudflare, a regular user will have no idea about what Cloudflare is and what they do. If something like the OP happens to them, they will just figure “the site is broken” and move on. So there could be a large hidden number of users who have suffered from overzealous Cloudflare blocking without being able to identify it as such.