Linux is super fragmented (and generally has been historically).
If more people in Linux agreed to develop, use, and support the same distro–similarly to how most of us use the same kernel–then that distro would probably be better than Windows and more people would move to Linux.
First off nobody can agree on anything, ever, so this is some fantasy world that will never exist.
Second, I’ve seen this complaint for at least 20 years and yet the Linux ecosystem is stronger than ever.
Fragmentation is a strength, not a weakness. There are amazing developers who would never have had the opportunity to contribute if development was monolithic like you are proposing.