These disagreements almost always boil down to one side saying "some people use React to build content-oriented websites" and the other side saying "but most of us are building web applications".

In a typical web application use case (yes, there are exceptions) you're only rarely looking at usage from old or cheap Android devices. Occasionally you'll see a tablet, but even that's rare. The vast majority of the time your users are on either Chrome or Safari on a relatively modern Mac or Windows machine. In many cases the application loads once at the start of at least 10+ minutes of work, so initial load times rarely matter much.

If you're building a website that needs SEO, then yeah, React is completely the wrong tool, and you should just make a proper static site or hook your marketing team up with WordPress (or whatever takes its place once Matt is finished blowing it up). But those use cases, while common, represent a tiny fraction of total engineering effort across the industry, so most web developers here don't have the design constraints that make React a bad choice.