The travesty known as "Perl 6" ignored that, and so it was ignored.

No, Mike. That wasn't the problem.

The problem is that it went for 15 years without any substantive release, and what was eventually released wasn't worth migrating to.

(Yes, I am aware of the first Rakudo Star. No, it doesn't count. No, I don't want to debate this with the gish galloper gallery.)