it's like gold. the more people have gold, the less valuable the gold is, because it's no longer scarce.
i don't agree that more university students devalue universities however. on the contrary, more university level education is in my opinion the best response to less jobs and automation.
we need ever greater and greater parts of our society in higher education to study, research and teach, because all the low level jobs will eventually be automated away.
but imagine what our society can do if we are all educated to the level of a college professor. with more educated people we can address issues such as pollution and climate-change much more easily, and this can only speed up the advancement of our society.