Earlier quoted context omitted.
Isn't this incompatible with Net Neutrality? I think Cloudflare already was against net neutrality, but people who believe in that principle might need to avoid Backblaze as well if that is the case.
No, this has nothing to do with net neutrality. Your ISP isn't discriminating what data you consume, whether it's from cloudflare or another CDN. This is about the fact that bandwidth is usually bought by capacity between networks rather than usage and they're passing those savings on to you instead of charging expensive per-GB costs like the major clouds.
If the argument is a semantic one, that net neutrality is so narrowly defined that it doesn't apply to them as a CDN rather than a conventional ISP, it still stands that the situation is not-net-neutral if we generalize that to include CDNs, which it ought to, since that's what the N stands for.