Earlier quoted context omitted.
> if the cost is an extra few milliseconds of render time and few extra hours of dev time That is very optimistic. Most React projects never get to the optimization stage, and end up with seconds of rendering and transition delays that significantly harm UX. And the amount of time spent battling hooks, re-renders, compatibility issues, etc amounts to hundreds of hours over the course of a medium-sized project, thousa…
“Most” react apps needing “seconds” definitely needs some citation or evidence. Even in fairly heavy and laggy react apps, it’s still usually network latency, waterfall requests, ad/tracking bloatware, large asset sizes, and the usual old classics that cause perceptible slowness in my experience.
I won't say most react apps performs like this. But it's what you will get if you ship a big react app without optimization at all.
Other framework mostly have a much saner default (for example, component without argument change does not re-render). So it will work well (not best though) even in large scale. But in react they are all opt-in.