I guess another controversial opinion: this is a problem with the idea of CI (or at least how we work with it and what we expect to get out of it), rather than the idea of randomized tests.
Flaky tests are an indicator of poor code: maybe it's your actual code, maybe it's a bug in the test code, or maybe it's external dependency + lack of error handling in the test code but there's a problem somewhere.
I did admit this was controversial! But it fits in with a more general view that there are a lot of tools which make good servants but poor masters. Auto-builders are a good thing, partly because (as you say) they can help to clarify what is required to make a build, and partly because (especially for dependency-heavy software, which seems to be the norm nowadays) they can help catch things quickly when the dependencies shift beneath you. Making them a hard gate on releases seems a little too close to making the tooling your master, though.
(Somewhat separately, I also worry about CI acts as a hiding place for complexity. Sometimes it reaches that point where nobody knows how to make a build without the CI tool any more. Then local testing and debugging becomes difficult.)
I do also agree that CI can hide complexity, but that's true of any tool as well as non-CI builds. Compared to a human running things, it's at least somewhat self-documenting due to being scripted.