I kind of agree it's increasingly annoying to find dead space on a titlebar, and I absolutely loathe Microsoft's use of the title bar to stick crap I have never and will never use. I don't search enough to waste half the title bar on a search bar, I couldn't care less who I'm logged in as, and "Saved to this PC" is nothing more than Microsoft flipping us off for having zero interest in automatically saving everything OneDrive.
At the same time, I really do like using the title bar as a tab bar. It's a decent compromise insofar as they're conceptually like mini title bars for each page we have open.
Round controls, however, need to die yesterday. Rounded, sure, but having a full semicircle wasted at each end of a button is just a gratuitous waste of space. "Compact" is fundamentally incompatible with "round".