As someone in the Apple ecosystem, Firefox is not a very compelling alternative. I've certainly tried: Firefox Focus was my main iOS browser for a few years (I know it's Webkit-based) and I've tried switching on desktop as well. On desktop, various Firefox updates would change my settings subtly and nag me about features I had no interest in. On top of that, it was simply a slower browser, both with DOM manipulation…
If I used windows or Linux I would probably give it a try again.