This is not the problem. You can easily use i.e. React and some related libs on mobile without slowing down the experience at all. Everything will be fast and responsive, loading times and the mobile site itself (if done right). The problem Google tries to address (and this is a real problem) are the cascaded ad networks on webpages which load hundreds of JS libs once a page is loaded. This is a huge problem and yes, it needs to be solved. Just go to any news site and open Chrome Inspector's Networking tab, then you'll be shocked about the millions of resources still being loaded. AMP is solving this by putting Google as the gatekeeper in front of all this networks. I am ok with this, those ad networks created the problem and I am fine if they now need to deal with Google's monopoly but I am not fine with being restricted in using JS in general because you can do it right, even on mobile.