Facebook's site is awful, but performance, and specifically the performance of React on Facebook if I feel like watching profiling reports in Dev Tools, is rarely ever my complaint with Facebook's site. (When I have noticed performance issues with Facebook they were network/backend issues, not front end issues.) Facebook seem to have some pretty aggressive performance goals, meet them more often than not, and React seems to benefit well from that dogfooding (as release notes have sometimes mentioned that performance improvements were driven by Facebook's needs).
Anecdotally, having to profile the performance of apps I've built on Angular and React I'd much rather be profiling a React app than Angular any day of the week. I got so frustrated with Zone.js at one point I wrote an entire "Component Framework" for Angular to avoid Zone.js as much as possible and try to remove Zone.js entirely as a dependency in Angular apps that I need to profile.
Anecdotally, having to profile the performance of apps I've built on Angular and React I'd much rather be profiling a React app than Angular any day of the week. I got so frustrated with Zone.js at one point I wrote an entire "Component Framework" for Angular to avoid Zone.js as much as possible and try to remove Zone.js entirely as a dependency in Angular apps that I need to profile.