by that metric shouldn't OSR/1e/TSR editions be separate from 3e and 4e... and 3e and 4e can't be more different. It used to be that way but those threads didn't seem a worthwhile thing to keep in it's own form. So we got legacy editions to combine them. now 5e is either STILL 1d&D version or a legacy edition... and thats the thing.
I'm sure ther are plenty of 3.5 fans that think there version should have it's own, and plenty of 4e people have asked for them to have there own... where is that line?