Surely there are great options, depending your needs, for example Ungoogled Chromium or Brave Browser, if you're looking for something that gives a Chrome-like experience, but without all the data gathering from Google (Ungoogled Chromium) or with some privacy-minded features already integrated (Brave).
There's also Waterfox, which is a Firefox fork (I can be wrong with this description! But that is how I understand it) that is still compatible with the old addons (XUL). There's also another project on GitLab named LibreWolf that it will be (or already is) a Firefox fork that (based on the Librefox project), in a similar fashion to Ungoogled Chromium), it has removed several mozilla-only features such as the integrated telemetry, and I think that also the "studies" feature. It also attempts to integrate some privacy-minded features in a similar way that Brave browser do. As the last time that I checked the project, they already have created some builds for Linux. I'm not quite sure if they have started to work on OSx/Windows builds.
I don't know which are your parameters to determine which browser could be better than Firefox, but it could help to take a look at those (and perhaps other) projects, use them for a while, and see which of them suits better for you.
Links:
Ungoogled Chromium: https://github.com/Eloston/ungoogled-chromium
Brave Browser: https://brave.com/
Waterfox: https://www.waterfox.net/
LibreWolf: https://gitlab.com/librewolf-community
Kind regards.