The only asterisk to that statement would be if OP was a Mac user. Using Firefox for reddit and youtube nets me 4 hours of battery life on a 2020 13 inch MacBook Pro, while safari will get my 6.5-8 hours with the same usage.
Some years ago Firefox was near-unusable on MacBooks because it started spinning fans like crazy after a few minutes, eating battery in 30 minutes. But it had improved immensely since that time.
Speaking of Safari, maybe it's a matter of preference or habit, but for me it's has a very weird UX
Blame apple