GNOME Shell to support a "classic" mode

Given your own description of the existing parallel installation capabilities your tone doesn't seem warranted. Depending on what you want out of such a feature defining core applications as part of "GNOME 3" doesn't seem to be a complete reach.
I realize that it is frustrating to see something you put loads of work dragged through the mud, but accepting that level doesn't help. It also doesn't mean that everybody criticizing is one of the mud throwers.