> You can be exposed to them, but without understanding them, and experiencing both good, bad, and really bad 'solutions' to them, and understand the impact (on the business, on the code, on security, on maintainability, etc)... you just can't really get all that in 2 years.

I don't think this is about becoming expert. This is about learning at least very basics in multiple areas so that you are not completely clueless and know issues exist. When you redefine requirements to "2 years active learning worth of knowledge", you moved goalpost quite far.

> I've been doing this for a bit over 25 years, professionally now, and... there's a lot I don't 'get' with current stuff. But I've seen and lived enough projects, in enough different situations, to have a good idea of impact of tech decisions, and to understand how to make tradeoff decisions.

This is being senior.