> But on the same subject all pages would be data heavy.
Not all of them. For a trivial example, an in-depth article about a topic would be penalized more than a more epidermic one, because it would contain more text, graphs, etc.
> For reference, I optimized my website a while ago and ended up with the average page being < 15K.
I feel you, I absolutely hate that my website uses a bunch of stuff for almost no reason. 80 KB of CSS or 90 KB of font isn't awesome, and I started a project to provide information on how to create lighter websites (https://www.lightentheweb.com/, stalled a bit).
All I'm saying here, though, is that the solution is more nuanced than "heavier = lower". AMP is definitely not a step in the right direction, though. I wonder if Google could give sites that used a specific CSS file and no JS a bump, rather than loading things on their own domain.