For my sins I occasionally create large PRs (> 1,000 files) in GitHub, and teammates (who mostly all use Chrome) will sometimes say "I'll approve once it loads for me..."
I actually have been trying to figure out how to get my React application (unreleased) to perform less laggy in Safari than it does in Firefox/Chrome, and it seems like it is related to all the damn DOM elements. This sucks. Virtualizing viewports adds loads of complexity and breaks some built-in browser features, so I generally prefer not to do it. But, at least in my case, Safari seems to struggle with doing certain layout operations with a shit load of elements more than Chrome and Firefox do.
By all means. It sometimes feels like React is more the symptom than the actual issue, though.
Personally I generally just like having less code; generally makes for fewer footguns. But that's an incredibly hard sell in general (and of course not the entire story).
But CSS has bit me with heavy pages (causing a few seconds of lag that even devtools debugging/logging didn't point towards). We know wildcard selectors can impact performance, but in my case there were many open ended selectors like `:not(.what) .ever` where the `:not()` not being attached to anything made it act like a wildcard with conditions. Using `:has()` will do the same with additional overhead. Safari was the worst at handling large pages and these types of selectors and I noticed more sluggishness 2-3 years ago.
Normally, you be able to debug selector matching performance (and in general, see how much style computation costs you), so it's a bit weird if you have phantom multi-second delays.