So the "movement" against modern browser features is not a movement and has nothing to do with these features but its simply a version of "kids these days lost their ways" thinking. A version of conservatism, I guess. "Everything was better in the good old days" and "The new generation is horrible, the humanity is doomed" kind of thoughts are probably a manifestation of fading youth.
Just kidding, back in my day kids assumed the same thing.
Also, this exact conversation has been happening since the web was created. Linked article is evidence of that.