Because it's overhyped to the point it's being used everywhere even for projects where there was no reason to ever go beyond basic static HTML + maybe vanilla js, if at all, by devs who want to pad their resume. At the same time, it taxes your mobile battery, and generally leads to a world of overcomplicated appified Chrome-only web sites when actually the web was meant as a straightforward mechanism for self-publishing and exchanging ideas. Finally, reading the umptieth take of a junior dev having his React epiphany, or worse, a staged React consultancy/course ad piece provokes counter-reaction, if only because it's intellectually insulting.