Like they wanted CSD and they decreed that everyone, even non-GNOME apps like old games that nobody works on should implement CSD because they are not going to be backwards compatible.
Same with notifications, old apps, third party apps should implement the GNOME way, they do not care for supporting non-GNOME stuff.
But more power for them, they self select a niche user, a "GNOME user" that either is compatible with the GNOME way or they will contort themselves into it.
And about this designers forcing their shit on users, I hit lately a issue with GTK apps where the windows of the app and popups are hard coded and you can't resize them. Because of my bad eyes I use a giant font size and this apps are unusable (I need to research if is possible to trick this windows at runtiem that they are allowed to resize)
Could you clarify what you mean by this?