It's not just functional approaches that solve the concurrency problems, but FP combined with strong time modelling constructs. If you are just using FP, but no

It's not just functional approaches that solve the concurrency problems, but FP combined with strong time modelling constructs. If you are just using FP, but not any kind of STM, then you are still going to have difficulties. Imperative languages have neither strong time constructs nor side-effect free approaches. So you lose twice. But just getting rid of side effects is not going to take you all the way to pain free concurrency. You need more.