The design of libadwaita is very reminiscent of the time I was at Apple. Around the time they decided to unify the codebase and lay off the entire OS X team and reorg it into a new software team. I noticed the design changes as part of dogfooding internal OS X versions and design changes were jarring to say the least.
In short, a product cannot be all things to all people. It should play to its strengths and delight it’s existing and new customers/users.