I feel like I'm not understanding what your saying. Zooming is easy. I have bad eyes and zoom in on websites all the time. Simple sites like LWN work great, but every "magically interactive overly-designed" site breaks immediately. Large icons start overlapping/fighting with each other and the text. Wide-margins end up squishing the site to one or two word columns
If you like gigantic fonts, feel free to press "Ctrl +" in your browser. I'm sure there's also a setting you can change to make the fonts larger by default if you're having problems with your eyesight.
> large icons, large fonts, wide margins
I have 20/20 vision but even for me, all these are boons. It's the "design types" that want small fonts because they look cool. But for reading, give me a 14 or 16 font any day of the week, much more relaxing on the eyes.
All those things you're complaining about improve readability and discoverability.
I can't even imagine how people with bad eyesight think about this topic...
> and slow response times because everything has to go through JS/XHR
This does, indeed, look like a (software) design fad.