Many years ago Firfox was very slow
It has improved enormously, obviously, but some people never forget
It is a lesson. Never take your eye off the ball. Firefox did, back in the day, and Google ate their lunch
XUL extensions maybe? The reason I gave up on Firefox after literally decades of using it was because they kept removing features I was actively using without fixing any of the problems. What's the point of using a niche browser if it is exactly like the non-niche browser, but with more compatibility issues?
I think its OSX and Windows people talking past each other.
On a Mac, Firefox is pale in comparison to Safari.
That said your average person isn't trying out every browser multiple times per year to see how fast it is today.
How does that help when you can't run uBlock Origin on Safari?
I don't use Safari because of the extensions and overall it's too basic for me, but not everyone is like you or me.
There is a third party extension for it but I'm generally reluctant to install browser extensions because I worry about security.
I'll give you an example that annoys me because I look at it every day: the bookmarks bar still uses the same margins as it did in Firefox 3, even after 2 major UI redesigns. Then we have things like windows from Firefox 3 for some stuff with pages that open on tabs and have a different UI. Like, pick one and stick with it.
CTRL/CMD+Click on a bookmark has a different behaviour than CTRL/CMD+Click on a link. No other browser does this.
Profiles are there, but there's no user friendly UI... and no, containers can't do the same things as profiles.
Then you have things like battery use on platforms like macOS, which is still worse for me than Chrome or Safari.
So yeah... it works, but it's not the best browser. I tolerate it mostly because of extensions like uBlock Origin.
I also use ublock origin in android which should make loading page faster I guess but unless the page is absolutely awful, chrome remains faster even with ads on.