I don't think it's valid criticism in the first place.
The kernel is only a single part of a much bigger "Linux desktop distribution". For desktop users, work on good default configurations for all software, X (or its replacements), window managers, package managers, backports of security fixes to old software, and many other things that Canonical does are just as valuable as improving the kernel itself.
The kernel is only a single part of a much bigger "Linux desktop distribution". For desktop users, work on good default configurations for all software, X (or its replacements), window managers, package managers, backports of security fixes to old software, and many other things that Canonical does are just as valuable as improving the kernel itself.