One of my hobbies while at Google (2010-2015) was to watch the multiple failed attempts to get rid of Borg Config Language and actual Python in Blaze. It took a lot of work until they eventually succeeded. You're probably underestimating the rigor, the pain, and also the value involved in cleaning those things up: being able to cleanly operate programmatically at scale in the Google monorepo is extremely necessary.
(This is also why I don't trust configuration languages built by people who _didn't_ observe the years of pain. Cue and jsonnet are notable projects that were able to incorporate a lot of lessons.)