If you look at the Julia issue tracker, you'll see an enormous amount of discussion between and with core devs about language design decisions.
It's good to have someone primarily responsible for the compiler, someone responsible for libraries, another for GC, another for the package manager, etc. I'm not suggesting every core dev needs to be intimately involved with every line of code or design decision. It's more about how the development process feels to outsiders. After all, the question that was asked was about why Nim is not being hyped, rather than why is it not a fantastic language (it is fantastic).
It is great to hear about two other (albeit nameless) individuals working on the compiler though.
I understand, that, if things the language uses are implemented in that language itself, the language design breaks them. But if not?
A language like Java could probably work without GC, give the dev a "free" method and be done with it. The whole language would look the same syntactically.
Fred Brooks would like a word...
More seriously, this is the important part:
> like-minded individuals who understand and agree on the core design goals,
A team who agrees on the big picture, but can work together to sort out the small details, is really important.
There's also balances between doing things quickly and doing things right. Sometimes, slowing down a bit gets you a significantly better end product. Sometimes it's just a slowdown.