I'm convinced that all the people repeating the mantra about memory and CPU use switched away a year ago and haven't actually tried a recent version. The alternative (to being ignorant) is that they are flat out liars, because anyone who has tried a recent version knows point blank that they are wrong.
Firefox is to Ford what Chrome is to Toyota. Even if Firefox is as reliable and efficient as Chrome these days, some people still see it as being the gas-guzzling unreliable Ford vehicle of yesteryear.