A bit of a shame how that basically good idea turned into "let's just fill the screen with pointless whitespace instead".
Are you talking about the fat window titlebars? Those are too big, imo, but I have removed them from foot, Firefox, and Brave. I don’t use anything else often enough for it to bother me.
For instance look at the settings app screenshots here, everything is surrounded by at least twice as much empty space then actually needed for no obvious reason (except maybe to prevent fat-finger-syndrome on touch displays, but I use a mouse cursor, thank you very much):
https://apps.gnome.org/Settings/
Look how few settings actually fit on one page before scrolling is necessary (and since there's no scrollbar it's not even clear in some cases that more settings are hiding below). It looks less a settings application but more like an example application for UI design mistakes.
I have the same beef with modern macOS and Windows UIs though (but GNOME definitely takes the crown of most weird desktop UI).
It's some sort of modern UI designer brain virus to waste valuable screen real estate with empty pixels (but not wasting space doesn't mean to fall into the other extreme to fill everything with clutter, UI design is a fine art of balancing functionality with aesthetics - currently the pendulum has been swinging way too much into the aesthetics direction, ignoring that UIs should be functional first, and pretty only second.