I do like the old JS Gmail UI. But the current JS Gmail UI doesn’t feel any slower. It is cluttered with more features, but some of them I find useful. (Displaying my calendar and being able to accept invites right in Gmail being a big one.)
As someone who used the HTML gmail interface right up until google pulled the plug: the JS version is much slower to load. Every morning, I get to have about 10 seconds thinking about how it used to be faster.
It absolutely is slower. To an extreme degree even. It takes 10 to 20 seconds to load and is incredibly sluggish to use on some low-end machines I use regularly.
I disagree that we should be optimizing for low end machines and holding back on product improvements for the 80% mass market. Technology improves, it’s one of its best traits. We don’t need to be stuck in the past.
I think those machines are super fun and a snappy Linux experience is very satisfying. I use a lightweight WM myself on Linux and prefer it over the heavy ones. But this segment is 0.1% of technology users and we shouldn’t constrain applications to the limited hardware that this population chooses to use.