Didnt know there was a cern tld
https://con.cern is not yet used, so...
It was a huge mistake, borne out of greed and recklessness.
They also screwed up some old URL/email parsers/sniffers hardcoding TLDs. Largely the fault of bad assumptions to begin with.
Other than the above, I don’t see much of a problem. Whatever problems people like to point out about gLTDs already existed with numerous sketchy ccTLDs, like .io. Guess what, the latest hotness .ai is also one of those.