You have to look at it from Blizz's perspective:
They can either make unique 5 mans that take extra development time to create fights, art, gear, lore, etc that are more accessible. Not to mention you could run them more often, and with friends exclusively, gearing you up faster and potentially unsub quicker.
Or they could copy/paste a raid instance where mechanics are nerfed into the ground, you know nobody (or close to it) in the raid, you have less chances at gear, and have a lower droprate chance as well. This slows the gearing process and potentially increases the likelyhood for players to stay subbed.
If Blizz wants to forget it's 8 year 5-man dungeon model in MoP for a chance to cut down on development and potentially make more money, why not?
IMO: The new 90 gearing progression is such a poor decision I can't even...