These are not some "whizzy bells and whistles" but extensions that provide important functionality for those who know and use them. And I have daily run two installations and profiles of Firefox ESR 52.9 with over 300 tabs or more open in frequent heavy duty use, and there have been no problems with apps not working, with only a rare web site not rendering. Which is no problem since a simply right click Open with and the other browser I choose does it. And with no viruses/malware in years, thank God. But the fact the minimalist Chrome, pretty much a sedan versus a utility truck, is by far the #1 browser indicates that most people just go with the flow or have no use for much more than some "whizzy bells and whistles" versus very useful enhancements.
You are making a false apple to orange comparison, i.e. comparing Edge without any extensions to FireFox with extensions.
The new version of Edge will support not only MS extensions but Chrome based extensions also. In my experience, there are more extensions and addons for Chrome based browsers than there are for FireFox.
Firefox is a memory pig. Always #3 behind Chrome and the New Edge for memory consumption and speed.