We grow down in sophistication in tech. Everything goes to the lowest common denominator, then it falls further. The web used to be sophisticated and it was only for nerds.
If its the middle ages and the only people who have learned to read are the very most educated part of the the population, then the average printed material is going to be intellectual. As the reading population expands over the next 1000 years, and the average book hence becomes less scholarly, you might naively conclude that everything is becoming 'lowest common denominator'. But overall, education standards + sophistication are rising hugely.
Sure, when only nerds could access the web, it was super sophisticated. And it had to get easier to go mainstream. But that doesn't mean the mainstream trend is to always dumb down forever, as you are arguing.
Apple mouse used to have only one button, but now look at the power of the multitouch UX almost everyone uses on their smartphone daily. Look at Gmail compared to Hotmail v1, Youtube compared to cable TV etc. Its easy to forget how powerful and sophisticated they are. People have learned to do really sophisticated things, create, communicate etc.
Sure, things dumbed down since only CS grad students used the Internet. But now that growth is slowing, I bet tastes are going to increase in sophistication again.
This only applies to surface complexity though. Under the hood the web today is many orders of magnitude more complex than the web in the 1990s.