Craig Hockenberry has posted an interesting proposal about limiting the amount of JS loaded by a web page. I understand that the implementation can be complicated but that’s not a reason to not try.
We could proceed step by step. Instead of building such limits in the browsers right away we could start with a simple extension that kicks in and tells you “This website is using too much memory/CPU”. It’s not a solution but it’s a good start to incentivize developers to be less sloppy.