> Maybe the 10% of companies that aren't deterred by this opinion simply don't have websites that necessitate a "web application,"

The further your features get from a static html page the less JS frameworks helps. For example you can pretty easily write super mario in vanilla JS using normal html elements for rendering, doing that in JS frameworks would not be very fun at all. However if all you want to do is display data from servers or let the user fill in forms then JS frameworks are pretty good.