Hasbro won't let D&D survive at niche market revenues.
So Wizards is forced to make D&D take the shape of niche market games (catering to specific playstyles) without losing their monolithic "flagship" status that brings in the big bucks because they're what everybody plays.
Hence their need to identify what is essentially "D&D" that they can retain (and thus retain their brand recognition as The RPG) while simultaneously learning how to provide a customizable experience (in order to, within a single system which a small number of developers can maintain, replicate the wider RPG market's multi-system experience).
They are, effectively, trying to encapsulate the breadth of the entire RPG marketplace within their own franchise, so that people buy their new stuff instead of trying other games.
You really have to admire the scope of their vision.
It takes some gigantic brass clangers to even come up with it, much less think you can accomplish it, and sell the idea to the bosses.
@shatterspike1 I recently came across the idea of "mature" game engines.
That is, the point at which an engine's potential has been explored, and any new content released for it may be creative, but probably won't be innovative.