Let's do a little rewording...
Concurrency is not a language issue for the same reason that it is not a checkbox that you can put on a feature list.
Correctly implementing concurrent program is a process. Many things that help concurrency can become language features.
Would you agree? I for one disagree. Shared state parallelism (threads) is a huge bucket of worms. Humans really aren't smart enough to use it correctly. What we need are new languages to help us manage concurrency.
Erlang and
Oz spring to mind. To my mind problems like that scream out
language issue. Same goes for security.