Many times I've heard that the best thing someone can do is to specialize in one specific field and that generalists will end up as jack of all trades, masters of none. Well, that's bullshit.
It usually takes 2 to 5 years to get really good at something (professional level), to become specialize. Obviously, the number of years necessary depends on the complexity of the field. But what is important to understand here is that once a person reached a professional level, then the learning curve slows down significantly.
In reality, after just 10-15 years of practice, while a specialist is only good at one thing, the generalist will be just as good at 2-5 things. And at the top of that, when we master another field, it makes us better at other things as well, because everything is interconnected. And the better you get at connecting dots, the faster your learn and master new fields. Big studios want you to specialize, because it makes you less valuable, so that way they can pay you less and you are dispensable.