Similar here. It's not unusual to be blocked from a site by CloudFlare when I'm running Firefox (either ESR or current release) on Linux.
I suspect that people operating Web sites have no idea how many legitimate users are blocked by CloudFlare.
And. based on the responses I got when I contacted two of the companies whose sites were chronically blocked by CloudFlare for months, it seemed like it wasn't worth any employee's time to try to diagnose.
Also, I'm frequently blocked by CloudFlare when running Tor Browser. Blocking by Tor exit node IP address (if that's what's happening) is much more understandable than blocking Firefox from a residential IP address, but still makes CloudFlare not a friend of people who want or need to use Tor.