Not my words, but those of Linus Torvalds!
Too many distros. Hundreds too many. There are maybe 20 popular, active distros and even if you boil it down to the most fundamental 3 branches using the Linux kernel, those three branches (SUSE/RH/Debian) don't just use the vanilla kernel. You literally download a precompiled binary application that matches your particular branch of Linux, or compile it yourself for the distro you're using. That's not user-friendly, it's not beginner-friendly, and it sure as hell can't be described as anything other than a fragmented mess.
Individual Linux distros like Arch or Ubuntu are decent, but the whole ecosystem isn't a cohesive, clean, easy-to-understand experience for most people. Torvalds was 100% right when he called it a fragmented mess.