Why? I feel like this is a bug. Firefox is supposedly ported to gtk3 since 2016: https://bugzilla.mozilla.org/show_bug.cgi?id=1186003 Can we drop this dependency? (Firefox-bin is the single last ebuild I use that depends on gtk2) Reproducible: Always
I just had a look to thunderbird-bin ebuild, and same applies.
It's needed by NPAPI support (which still uses gtk2 underneath) that will "likely" get removed late this year or early 2021. https://bugzilla.mozilla.org/show_bug.cgi?id=1377445 Although when it comes to firefox-bin, simply removing the libraries should allow to drop the dependency (along with NPAPI/flash support), albeit "personally" not convinced it's worth introducing short-lived USE flags, warnings, or dropping features early by default before Mozilla does it themselves.
Sounds reasonable so, ok, thanks. Closing