Oh, I definitely agree that Hinterlands is really geared towards experienced players only in a way that surpasses even Alchemy. The cards are more complex than what we've seen before, and incredibly non-obvious in their strengths and weaknesses, and while many of us (myself included) here love and want that stuff, I don't blame more casual players for being turned off.
So, complexity creep for sure, and that's only natural. But, interestingly, not power creep: I'm seeing a lot of situational cards and very few if any must-buys. Cornucopia was actually an incredibly powerful set of cards, with fully half the set absolutely elite and the other half still pretty good, and Prosperity and Seaside were both also much much stronger than the base set. By contrast, it really seems that Hinterlands has dialed the power level down several notches: even the vaunted Crossroads is, I bet, going to very often be a bad buy.
Given how strong the past few sets have been, I think this is absolutely the right thing for the game, by the way.