I didn't say they delivered perfectly either; i3's minimalistic nature isn't really well suited to a holistic approach to tabbing, either. I just said that it delivers on the concept at all.

My frustration, fundamentally, is that I don't want every app that wants to use some kind of tabbing interface to be different. Use different shortcuts, different models. I would rather the WM/DE provide a holistic approach that can be inclusive of all or at least most of the basic needs you keep listing, and that could be applied to other programs in a uniform way.

That's beyond the imagination of Microsoft apparently (I agree that just making taskbar items clump isn't the same), and beyond the scope of an x11 WM (which doesn't have any meaningful say over the client area of any program on its own). But it's not impossible, and it's not "the wrong way" just because no one's tried or managed to do it yet.