So lets say I want to start my next web project in Janet. I already know Scheme and can probably quite easily just start writing another lisp, assuming it has TCO and I can do things mostly like I would in Scheme, except maybe for having to use funcall (which is annoying, but OK). Does Janet have libraries, that enable web projects? Like a web server and SXML or something like that? Or does it have things like a JSON parser? All these little things one would like to have, to not have to develop the basics first, before getting to the actual project.
And what about data structures? Are there functional data structures available? In GNU Guile I have at least the unmaintained guile-pfds. Hopefully, I will one day understand enough about functional data structures to build more or to maybe even maintain that library. But learning resources are scarce. It is already difficult to find a functional version of an AVL tree! Lots and lots of places merely teach non-persistent, non-functional versions of these data structures, and it is not trivial to translate them, might impact performance in ways that are not necessary, if one had great knowledge about how to make these data structures.
And also reproducibility! With GNU Guile I have what I need on Guix, which is great! With other languages, I might need to rely on older package managing approaches, that do not have reproducibility/determinism as the a high goal on their agenda, or might even lack the ability to create lock files/files with checksums. I don't want to go back to non-reproducible.
I am also eyeing statically typed variants like Carp. Same questions arise. Some seem really great and I would probably enjoy using them a lot. Would be a pity to then discover, that the ecosystem is just not there, and one has to create all the basic tools one needs oneself. Sometimes that can be fun, but it can also be exhausting and one never gets around to ones actual project.