In general, I wouldn't say that it's depressing. There are elements of it that are...less than savory, definitely. M:S to me is one of them. That attraction in particular feels like it was hugely popular for the first year or two, then it fizzled out. The Imagination pavilion needs a total overhaul, TT, unfortunately, is just weird and seemingly has no real theme (plus I can't get beyond the fact that you design a car yourself then 6 of you are all testing it simultaneously throughout the ride).
I think what the OP is touching on is that Epcot used to be be EPCOT, meaning it used to approach ambiguous scientific topics and develop a ride that was unique around them. Horizons was just Horizons. Sure it was sponsored by a company, but it was a ride unto itself. It was executed well and was geared to spark guests' creative imaginations. Same with UoE, WoM, etc. Nothing was movie-themed or linked to characters. Granted, SE, M:S, The Land, and WS don't have too much to do with movies or Disney characters. But there was something refreshing in the approach Disney took to look at human ingenuity and science in a way that was hopeful, educational, unique, and non-Disney-themed. You have to wonder: WoL, for example--would that still be popular if it was open and slightly updated today? Perhaps. But chances are we'd be seeing tie-ins to the new "Inside Out" movie creeping in and potentially re-theming the pavilion.
So, if that's some of what the OP was getting at then yes, I do agree that it has become depressing in that sense. But, Epcot isn't immune from encroaching commercialization and I think as time goes on, we'll be seeing less of EPCOT and more of Epcot.