The author is right. It just sucks to read what's true. He's not entirely right but he's on the right track.
You'll find a lot of tiny companies with dev. blogs where they explain in-depth the scaling strategy of their unknown, sporadically-used product.
Yes, react and vue are a few hundred kb gzipped. But are we seriously going to pretend that projects built with react are in a few hundred kb range? You can't even predict how big a project will be. It's not react's or vue's fault, it's simply how it is - add assets, add css, add additional libraries for <insert reason here> and it's not unrealistic to get 2-3 MB that you need to download.
A lot of people are designing their products to show off to their peers or for google (SEO). Users get left out. And we (users) are starting to feel it. Heed the warning or turn the blind eye.