Firefox on macOS is fine. I've been using it as my primary browser for years. I consistently get captchas on archive.is (and just verified I also do on Brave),

Firefox on macOS is fine. I've been using it as my primary browser for years. I consistently get captchas on archive.is (and just verified I also do on Brave), but rarely see it elsewhere. I don't know the cause of what you're seeing, but it's not simply Firefox.