Yes, I agree. To fail to register as the default program for all the extensions you support, ideally optionally, is surely the fault of the installer not the os?

There are perhaps better anecdotes for reasons to dislike windows...

Im not sure if libreoffice is fully to blame, I don't think it is possible for applications to _change_ the default app directly themselves, they now need to link to the windows settings screen to have the user manually do it. It is a fair point that libreoffice currently fails to do even this.

These are still registry entries and are still located in the same part of the registry and still with the same way. This hasn't changed. What's changed is registering applications to show up for the new UI is a huge pain requiring multiple registry keys, however simply setting the opening application for a given filetype/protocol is quite easy: either open a .reg file with reg.exe (pops up a code window) or regedit,exe (pops up a prompt), or add the entry programmatically (silent).

Personally, I'm still annoyed that removed the File Types settings in Windows 7(?), though some of them have made their way back with the new settings.