I don't think it's heavy language lock in at all.
If I need to do something in Python, I have options like pyrlang[0] and rabbitmq[1].
In fact, parsing in Elixir is not nearly as mature as what is provided in Python. I need to parse emails. Python has `email.parser` which is perfect for my use case. I can easily use Pyrlang to do this. But Elixir is still much better at being an email client (or many email clients). The end result is an email client in Elixir that uses Python to parse the emails.
When I started with Elixir, my goal was to use it as much as possible, but delegate as soon as the task is better handled in another language.
[0]:https://github.com/esl/Pyrlang
[1]:https://www.rabbitmq.com/