>We don't need 20 window managers, just 1 good enough one.
Would you like a window manager with 10-pixel-high title bars, which automatically positions windows in a tiled layout, which can be rearranged using the vi keys?
Perhaps you would. I wouldn't have it any other way.
But given the relative popularity of metacity and kwin, I suspect that most people would disagree -- and that is why we have 20 different window managers. Because nobody agrees on what "good" even means, let alone "good enough".