And for an extremely large number of honest users, they cannot realistically avoid this.

I live in India. Mobile data and fibre are all through tainted CGNAT, and I encounter Cloudflare challenges all the time. The two fibre providers I know about use CGNAT, and I expect others do too. I did (with difficulty!) ask my ISP about getting a static IP address (having in mind maybe ditching my small VPS in favour of hosting from home), but they said ₹500/month, which is way above market rate for leasing IPv4 addresses, more than I pay for my entire VPS in fact, so it definitely doesn’t make things cheaper. And I’m sceptical that it’d have good reputation with Cloudflare even then. It’ll probably still be in a blacklisted range.