[kunley]

Not exactly true about "performance is more API based". Everything adds up. 400ms here, 700 there. Websites can be slow even before api calls are triggered or on the middle of them, or while the results from api responses are presented.

[undefinedzero]

Rendering performance can definitely add up, but rarely do React websites render so many elements that you get to 700ms. Once you do, you can nearly always fix that with an performance optimizations iteration. I reckon that issue is just as likely in all frameworks, and less likely to be about React using 0.2ms (or something like that) longer per element to render before optimizations.