Lately, major vendors (with Edge, that includes Microsoft) are agreeing on standards, developing them FAST, and the web moves forward faster than it has ever moved. Long gone are the days where your standards can get stopped for multiple years. And vendor prefixes are less prevalent now as features get implemented properly sooner.
https://ishoudinireadyyet.com/
https://www.webcomponents.org/
Also, to use those standards, one needs to have access to latest browser versions, which never happens beyond controlled environments.
So typical web development always needs Modernizr, Babel, Polyfills (when possible) around.
Your argument makes no sense in the year 2018.
Of course if they just stick with the ideal model of hypertext documents, with a little bit of JS, it doesn't make sense.
As for web apps, I am ok with them, provided they run on the browser I have already installed, instead of faking native apps.