1. If you managed to learn a paradigm as arbitrary and unprincipled as OOP, learning pure FP should be a walk in the park. I find it an odd argument to put in the way of progress. Anecdotally, I have not heard of anyone regretting to learn FP, let alone going back to OOP. I would love to hear from people learning FP first, how did you find learning OOP as a second paradigm?

2. I've never found a need for (automated/annotated) dependency injection in FP. In languages that support it you can use type-classes for the most part or just add another function argument / close over state, or user a `ReaderT`, or most likely a combination of the above.

I'd say the only way to understand how useful and applicable FP is, is to go learn and use it for a while to solve actual problems. I found most things you think you'll miss you won't ever end up missing, because you actually never needed them in the first place.