I wouldn't say Firefox sucks but there are definitely some things that made me use Edge occasionally back when I used Firefox as my main browser. It was mainly stuff like a webpage that doesn't support Firefox and extensions not having a Firefox version. Which sure aren't problems with FireFox, it's more a problem of it not having enough adoption, but to an end user if the thing they wanna use doesn't work in FireFox but works in Chrome then that's FireFox's fault.