The asymmetry between developers using powerful new machines and not noticing performance is terrible for the average user is often mentioned, but I've noticed something else with React:

A React bundle in development, especially with StrictMode, has *way* worse performance, because it's doing a lot of extra things to make the development experience nicer, stuff like rendering *every change* twice, to check for consistency in pure components.

This makes it a lot easier to notice (and debug) performance issues that might not even be noticeable in production builds, or only on way lower specced hardware