Will anyone really understand the language?
As the language grows, it (by nature) becomes more complex. The C language (for example) is described (an older version) in a book by the originators (K & R) that is only a 1/2 inch thick (I just measured it!). C++ in its originator book (from a bunch of years ago, I don't have it in front of me, but Bjarne DID sign my copy) is about 1.5 inches thick. Given this the language is at least three times as complex, and getting more so. Most "modern" languages (I include C++ here) are getting more complex by the minute, and they are getting too complex for one person to "know" without propping open some sort of reference. The problem is that the complexities are getting ignored and people use a "known subset" and fake the rest of it.
Of course it gets worse when you need to link against some library, and (in C++) everything gets redefined because the author that it would be "cute". Then you attempt to learn another set of exceptions just to get your "simple task" done. It is a never ending task.
Of course it gets worse. A book on python (Programming Python by Mark Lutz) is even thicker (a good 3 inches) and learning the language is even more difficult. It is a never ending task.
As mentioned before "The nice thing about standards is that there are so many". To which I add: "and they are getting more complex!"
I long for the Fortran 66 (an improvement over Fortran II) days, but that is just me.
Yes, I did program a machine with Fortran II as its most complex language. It was a while ago!