Ironically does the Mythical Man Month already predict how a "second system" becomes overloaded and impossible to implement

From the beginning, the Perl 6 folks were well aware of Brooks' famous aphorism, even using it in their slogan (Apocalypse 12):

The official unofficial slogan of Perl 6 is "Second System Syndrome Done Right!"

From InfoWorld Larry Wall Interview (2015):

So early on, our slogan, or at least one of them, was "Second System Syndrome Done Right." And how do you do that? Well, you just have to take long enough. Companies can't do that because they have a bottom line and a burn rate. But we're an open source community, not needing to make a profit, only to do good in the world. So you know the saying, "Good, fast, cheap: pick two." Well, by definition our community has to do it cheap, so the saying reduces to "Good, Fast: pick one." And we quite intentionally picked good rather than fast.

See also: Three Tales of Second System Syndrome (Perl 6, Python 3, PHP 6 circa 2015)