It is. That's why I dropped Firefox.
It used to be slow for me, but now on the same hardware it is fast enough that I don't see any difference compared to chrome.
It runs noticeably faster than chrome on my 12 year old laptop. Plus, it isn't riddled with invasive tracking garbage.
I never saw a situation where the actual engine performance mattered in real world scenarios.
These days, all the engines are comparable, except that Google sabotages safari and firefox on its own sites.
I'm on a mac if that matters