Easytag 2.3.7 was released. A version bump would be nice. I'm not very familiar with the system, but as far as I could see, the gtk2 interface and it's configure switches have been removed. I had only one problem while re-using the old ebuild: The gnome-settings-scheme was not compiled. Reproducible: Always
Please bear in mind that the 2.3 series is a development series, running up to the eventual (future) 2.4.0 stable release. There should not be many changes between 2.3.7 and 2.4.0 (there is a crash fix and a build fix in git), however.
https://gitweb.gentoo.org/repo/gentoo.git/commit/media-sound/easytag?id=9e0426f0b0345675926e1635d440f429a0ec1fad