E3 vs Retail version

Demo was on a high-end PC, but the final build needs to run on the base PS4/Xbox One. Also imagine how much shitter the awful load times would be with better image quality.

Usually the downgrades are a combination of performance optimization and cut or changed features. E3 demos are often limited alpha or pre-alpha versions of the game run on high end PCs. In Anthem's case the original quality might have been fine in that environment with one or two characters, but on a console or minspec PC and ship level content it probably didn't run at target fps. For example, those volumetric clouds look great but no matter how they were implemented were probably expensive, so they got cut and replaced with cheaper billboard clouds. One thing that people who are not game developers need to understand is that games, at every step of the process, are smoke and mirrors and have constantly changing requirements. Developers aren't "lying to you" and trying to deceive you. Game teams definitely want to hit those original E3 targets. I've written features for tradeshow demos that haven't shipped or got completely rewritten after the demo in order to work for performance and gameplay reasons.

I understand the smoke and mirrors part, but my original question relates to(consoles aside): The presentations are done between 2-3 years before launch. Is it that a mid to high end pcs in 2018 aren't as good as the ones in the e3 presentations a few years ago? Are the demos aren't made to show case capabilities, just to motivate people to buy the game?

Even with the downgrades Anthem is still one of the best looking games out right now. Lots of other issues for sure, but visuals / graphics are definitely not Anthems downside. The game is gorgeous. Every game changes a bit from E3 demo to launch.