They aren't really dropping Firefox, they are just dropping the official build for a custom one: https://f-droid.org/repository/browse/?fdid=org.mozilla.fenn... It's no different that Debian with Iceweasel.
Not so correct. debian's Iceweasel is a little squabble about the logo not being licensed correctly. they only divert official version to add the -debianXXX when they backport security patches on the stable branch. They never removed anything. apart from branding. They even upstreamed the branding agnostic flags so they don't have to change even that! FDroid's fork is now a move against binary blobs. And copious trac…
You seem to be implying that Debian's Iceweasel package contains binary blobs. That shouldn't be the case, could you clarify that please? It's true though that Debian doesn't have policies about software using non-free network services and user tracking.