At the end of the day, whether you contribute to the power structure, as you put it, these are corporations, the money makes decisions, and they will gladly screw you or I if it came at an increase in expected profit. I am of the opinion that pre-orders could be made illegal next week, they will just calculate how much that costs them, and create very appealing microtransactions, gather and sell more data, or have more product placement/ads. If having me killed would increase their profit at no risk to them, I'm sure at the least one person on the board of shareholders would vote for it to happen. Targeting pre-orders is treating a symptom not the root cause. There are lots of great small indie groups that I am sure value customer satisfaction very highly. Too bad we want massive million polygon immersive worlds with professionally written stories that are created with the most recent cutting edge technology, which is something those indie developers can not do.
To respond directly to your idea of demos I think that would be cool, but I don't see it being implemented apart from near-release-date betas, which some games are doing now. The development process often doesn't go by linearly, so they could be 3/4 of the way through development and still not have a playable game. And with primarily story oriented games, they would have to restrict so much content for it anyways, so I see things like demos/betas to be more prominent in games like Overwatch and Player vs Player oriented games.
As for being frustrated with people paying an unnecessary fee to be disappointed, I wouldn't worry too much. I am financially stable, and don't really care much for the graphics 'downgrades' that we see from E3 to release. When I pre-order games sometimes I get disappointed (Watch dogs) but I know people who loved that game. If people really are perpetually disappointed with say, Ubisoft games, I would advise them to stop buying Ubisoft games. For those of us who do enjoy them, in all their graphically downgraded glory, I can't see why we are morons.
That being said when some developers do potentially forego some profits to stick to their vision for their game, and to ensure users have a great experience, I respect that a lot. If every company would do that the game industry would for sure see some positive changes, as long as we the players found a way to keep the money flowing. And if Ubisoft can give a lot of users great experiences, while disappointing some, while making enough profit to keep doing so for the foreseeable future, I'm also okay with that too.