As many buttons as he thinks he needs, and as a compromise they can be disabled by default and enabled through settings. Instead your ilk will probably remove even those remaining buttons and replace them with some obscure movement command
I have a pretty strong oppinion that GUI basics must be simple but more advanced stuff (e.g. tools that trainee professionals spend most of their workday in) must not hide its raw power because the user can be expected to learn.
User interface essentials have to be understandable without mental gymnastics by default without appearing overwhelming. The overwhelming majority of computer users don't change defaults on most software and a shockingly big number of computer users deal with them only because they must, not because they derive joy from it. They don't engage deeply with these devices at all. So those defaults must be picked carefully to keep the UI approachable. This isn't the same as ripping out features or antagonizing power users that do bother to learn.
using the titlebar for moving a window is extremely backwards and productivity killer.
that being said, I agree with you, and I think its an outright abomination to put the tabs in the titlebar, and its disgusting how crome and firefox by default removes the real titlebar
in either case, that appears to be the very extreme minority of cases you have to move a window
It also allows you to use it with win-drag of course.