Losing users is always a bad thing for the open source ecosystem. Lost users means fewer bug reports, fewer patches, fewer donations, and less support from paid developers working for various corporations (easy to forget but there are people whose job is to maintain open source projects like the Linux kernel). Fewer users means less incentive for hardware companies to provide any support, even just minimal technical documentation, needed for open source developers to write drivers (let alone contribute to that).
Forks require a significant commitment of time and effort, and really should be considered a last resort. The time commitment is much greater for prominent projects that receive a lot of activity like Gnome or Linux. Most users, even those with the necessary technical skills, do not have enough spare time to maintain a fork when things break.
Your dismissive attitude is fine for a obscure hobbyist project with a dozen users. It makes no sense for desktop Linux distros that now have many millions of users.
Part of the joy of open source are the freedoms it gives you, including the freedom to fork a project that doesn't meet your needs and make it so that it does. This works as it should pretty often - look at the gnome2 forks, the systemd-less distros etc. There's plenty of choice out there, and plenty of opportunity to get involved.
If you're unwilling to exercise those freedoms, then you're just whining about the stuff you're getting for free.