Dude, you're being awfully argumentative and defensive. You like the Druid as a full spellcaster- good for you!
But it's not like the Druid has ever been the most popular class.* There are a number of reasons for this- standard ideas of D&D as a "dungeon crawl," and thus leaving little room for outdoors specialties. Lack of great "druid" archetypes in fantasy genre literature and film. Maybe it sounds too much like dude? The druid abides?
But your argument about the history is also self-defeating. I mean, the druid WAS a subclass of cleric. That's the "origin" of the druid. What we would now call a domain. Druid is to Cleric as Illusionist is to Wizard (Magic User).
But speaking only for the tables I have seen, people either want to play the druid for shapeshifting, or don't want to play it. Your fun is different, and that's cool. I am simply noting that I happen to agree with what Mearls wrote. You disagree. So be it.
*In Dungeons and Dragons. People choose differently in different games; Diablo and WoW are, of course, different games.