Firefox does have some distinct features that are important to me. I want to open links from Gmail or Inbox without being logged in to my Google account. Firefox containers are perfect for that. I also like snoozing tabs and quick tab switching by typing % into the address bar.

Some of these things can be done in other browsers using third party extensions, but I am extremely reluctant when it comes to third party extensions for security reasons.

[Edit] Very important to me as well is built-in reader view.