Well if you stay on rawhide always you can get that rolling effect.
I am a little confused about the meaning, Ubuntu is using Unity. In addition to that, Ubuntu always uses more stable options. To tell the truth I have no idea where this all comes from.
Libreoffice in particular is available as flatpak. Fedora is unstable enough as is, it doesn't need new even more unstable software in my humble opinion
Major version upgrades can bring additional bugs with it, I think there are users appreciating more stable approach. I strongly believe there is a good reason why RHEL is sticking with ancient versions and is solely backporting fixes
Kernels are rebased when older kernels are not being actively maintained anymore, e.g. receiving fixes and security upgrades. It would be too time consuming to backport pathes to those older kernels like they do in RHEL.