[hombre_fatal]

That doesn't make sense except for a few heavy applications of JS like a resource-intensive web game which is obviously a niche outside of general statements about the internet.

Your 2017 Android isn't unusable because it can't run AJAX and $(dropdown).toggle() fast enough. Maybe it's not as fast as your laptop.

[pferde]

The issue here is that nowadays "heavy applications of JS" are quite common on blogs, news websites and other "definitely not web applications"-type of websites.

With JS enabled, I sometimes see simple mousewheel scrolling slow down or become choppy, or spiking CPU usage for a second or two. Simple scrolling of content that is already rendered and is not moving. And often, the same site with JS disabled scrolls smoothly (or completely fails to load, it's a crapshoot, really).