I can't find it now but I recently saw a graph of new Debian Developers joining the project over time and it has sharply declined in recent years. I was on track to becoming a Debian Developer (attended a couple DebConfs, got some packages into the archive, became a Debian Maintainer) but I ultimately burned out in large part because of how painful Debian's tooling makes everything. Michael Stapelberg's post about leaving Debian really rings true: https://michael.stapelberg.ch/posts/2019-03-10-debian-windin...
Debian may still be "getting by" but if they don't make changes like this Git transition they will eventually stop getting by.
I don’t think it’s a bad move, but it also seems like they were getting by with patches and tarballs.