I've personally worked on "simple" sites that actually had to do a ton of state management for user analytics and lead tracking purposes. (Whether or not all that tracking was necessary is out-of-scope for this comment...) It was pretty painful in a thin client; we were using PHP and jquery when I started. Even though the sites barely had any user-directed interactivity, I was really glad to migrate to React. Essentially I was able to shift my mental model of the site from content wrapper to software, and focus on how it could accomplish tasks, with content wrapping becoming fairly automated.

In our case that was useful because it aligned with our business goals, although I didn't particularly care for it. I wonder how many bloated, React-cargo-culting sites are actually not using that bloat, vs using it for user-invisible and/or user-hostile purposes. Are devs out there building personal blogs as React SPAs still?