You look at glaring examples like EA, and it's obvious that some companies simply don't have any respect for their customers to begin with. Thinking ill of our mental capacity is beside the point, I think. We're meat bags with wallets and feet to them, they couldn't care less what we think or feel as long as they can find a reliable way to get the feet moving in their direction, and certain individuals or committees have the power necessary to force anything into a project that they perceive correlates to increased wallets or increased moving feet.
The only reason they are making dumbed down games is because people are buying them. The problem is that gamers want what's new even if it's not what they would really rather be playing. It's not because a bunch of us are idiots, it's because a bunch of us get bored easily, or we're impatient, or we have a lot of disposable income and don't give a fuck, or we have jobs that make us care more about escapism than challenge. I know I've had 2 or 3 80 hour weeks back to back this past year, and when I got home after a 16 hour day I couldn't give two shits about whether Dishonored had objectively worse stealth mechanics than Deus Ex, I just wanted to run some bastard's neck through for a few minutes before going to sleep.
The hard truth is that in order to affect the change many of us would want in the industry, we need to vote intelligently with our wallets. We need to be honest with ourselves though about how hard that is, or whether we really care enough. Would you really rather go 2 years not playing anything new if it was sending a message to publishers that we won't consume your lazy AAA checklist title?
Of course, the really bad news is that even if you only bought the kind of games you wanted, some companies (let's stick with EA for now) still wouldn't get it. They could make a deep, challenging game if they wanted to, but the people throwing money around fundamentally don't know what that even means. If people went out and bought nothing but, say, Tetris for the Gameboy, all EA projects for anything but the Gameboy would be cancelled overnight. They would invest millions trying to figure out why people suddenly liked Tetris on the Gameboy, would invent some bullshit soundbite-sized corporate lingo phrase to call what they think that reason is (while fundamentally still completely missing the point), and the next Dragon Age game would be monochrome with big chunky blocks, combat would be 6 different puzzle games cobbled together, and there'd be microtransactions for different patterned blocks.
Edit: Dammit, I hate when I ramble.