That article by mfiano focuses on reasons the author switched from Lisp to Julia. As for the "loners" part, mfiano says this:
> This hints at a very real problem with Common Lisp: it has a tendency to attract people that employ the 'NIH syndrome' and refuse to collaborate. There is a large overlap of software available, and there is a large selection of low-hanging fruit for new developers. This coupled with the fact that the language is small, relatively speaking, hurts the language immensely.
Contrast this with how djha (TFA) puts it:
> I feel like Lisp is custom built for high functioning, high quality, low-head-count teams. I kinda feel like most of my projects into this category.
So TFA is kind of taking liberties with mfiano's post. I might come down to whether or not you view NIH syndrome as a net positive or negative.