Exactly what I've been worrying about for a few months now [0]. Arguments like "well at least this is as good as what humans do, and much faster" are fundamentally missing the point. Humans output things slowly enough that other humans can act as a check.
I've heard people working in construction industry mentioning that quality of design fell off the cliff when industry began to use computers more widely – less time and less people involved. The same is true about printing – there was much more time and people in the loop before computers. My grandmother worked with linotype machine printing newspapers. They were really good at catching and fixing grammar errors, sometimes catching even factual errors etc.
That's a good point. I'm talking specifically in the context of deploying code. The potential for senior devs to be totally overwhelmed with the work of reviewing junior devs' code is limited by the speed at which junior devs create PRs.
[0] https://news.ycombinator.com/item?id=44743651