If Social and Exploration aren't given actual design space and rules to play with that make them more important, then, when the DM decides to do a combat-light game and focus on the Social and Exploration pillars, what the DM is actually doing is either mostly freeform roleplaying (because currently ability checks with skill training bonuses are the only rules attached to those pillars), or homebrewing his own rules to support the playstyle.
Either way, regardless of whether that DM can make that game fun, it's a failing on the part of Mearls and his design/development team. They keep coming back and mentioning the three pillars, and I think that's a very novel approach, especially to D&D design which has sorely lacked Social and Exploration mechanics, yet we have seen no evidence that D&D Next will actually provide mechanics to run a deep Social and/or Exploration game.