I've been using Firefox exclusively for years. I have no idea what these people who say it breaks sites are talking about. If you absolutely need to use chrome for something just keep chromium around for that specific site.
Firefox is a decent browser. Some sites are coded like shit and then they futz around until it works in whatever Chrome your cousin used for development.
There's some very specific sites that are broken in non-chrome browsers. Writing this message took you more time than you'd spend starting chrome specifically for them for the next few months.
I see you managed to avoid encountering the Great ActiveX Catastrophe. Microsoft successfully managed to lock thousands of services behind proprietary extensions that only IE supported.
Also, IE wasn't technically garbage. There were a few, specific things wrong with it. Its main issue was that it implemented web features idiosyncratically, and Microsoft didn't document it, so you had to learn all of IE's "quirks" through trial and error: but apart from being undocumented, few of IE's idiosyncrasies were actually bugs. Its box model, for example, was arguably superior to the official W3C recommendation.
Removing ad blocking is what breaks the internet for me. Firefox is working 99.9% fine except 0.1% of site which I usually do not miss or in the worst case open in another browser. This is an insignificant nuance compared to the constant distraction of not using an ad blocker.