Those gatekeepers might not accept a John Carmack or a Palmer Luckey (or Bill Gates or Larry Ellison or Vitalik Buterin, etc, etc), but how many of their certificate-holders have done any comparably significant engineering work?
Does it matter for them? Would any employer/investor, seeking to hire/fund carmack etc hold back because they didn't have a cert? The vanishingly few with those levels of talent stand out quite easily and don't need "proof of competency" to be evaluated.
For the _vast majority_ of others, certification allows employers to have externally-validated trust in an engineer who mightn't stand out as obviously.
Early in their careers, even exceptional people face obstacles from gate-keepers. It wouldn't surprise me at all if there have been Germans of similar temperament, credentials and talent as Carmack or Luckey but who struggled much longer to stand out to a sufficient degree that they could get great job opportunities or funding in a that much more credentialist environment.
I like to imagine that such people would have found a way to emigrate and make their impact abroad. Either way, the cost to Germany itself (and Europe generally) has been immense.
Those gatekeepers might not accept a John Carmack or a Palmer Luckey (or Bill Gates or Larry Ellison or Vitalik Buterin, etc, etc), but how many of their certificate-holders have done any comparably significant engineering work?