Sure, any code base can be horrible to learn, but two equally well written code bases, types can help significantly. When your new employee can be confident that changes something in one place, won't invisibly break something in another place, they are more prone to start making changes.

Vimal Kumaar touches on how it has helped them get employees contributing to the code a lot quicker, after they moved to PureScript https://www.youtube.com/watch?v=HLEwYghBjo8 (I think around 24+ minutes in, but I recommend the whole talk).