I really think the biggest problem that new languages have is contending with the colossal hegemony of three stacks: C, Java, and Javascript.

There are a few exceptions, but for the most part, your language is going to be successful to the degree that it can interoperate with these environments. Common Lisp, Racket, Haskell, OCaml -- all of these languages have ffis, but they're "begrudging" ffis. They don't really care about your "legacy" systems or the titanic number of C and Java libraries that already exist.

Clojure and Scala do care about that, as does Lua. And Ruby and Python (and Perl) care as well.

I see beautiful new languages every day. I can tell whether they're going to live or die primarily on the basis of their attitude toward the dominant library environments in modern programming.