This is one of two packages forcing old numpy: <dev-python/numpy-1.9[${PYTHON_USEDEP}] Please look into making it work with newer numpy versions.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c83b48420b7ee012f156338a86b6f976519019c9 commit c83b48420b7ee012f156338a86b6f976519019c9 Author: Aaron Bauman <bman@gentoo.org> AuthorDate: 2019-12-08 19:01:43 +0000 Commit: Aaron Bauman <bman@gentoo.org> CommitDate: 2019-12-08 19:19:14 +0000 profiles/package.mask: drop last-rited pkgs Signed-off-by: Aaron Bauman <bman@gentoo.org>