You make an excellent point about the primacy of the community. I can't remember where I first came across the idea that languages are communities, possibly Richard Gabriel's Patterns of Software.

As someone about to embark on the Standard ML learning curve (motivated primarily by Ur/Web - Ur is a ML-like language), it is striking that the SML community is fragmented to the point of non-existence (not even a Planet SML, the sml-list is dead, & the SML subreddit is pretty lifeless).

Looking at Alice ML which has significant advancements over both Objective and Standard ML, it has great features, but no momentum which isn't helped by the fact that there hasn't been a release since 2007.