One of the most common pieces of advice for someone trying to get into the industry is to specialize. Larger companies tend to have large staff that are thoroughly compartmentalized; char artists, env artists, etc. So the idea behind the advice is that instead of trying to master a wide array of subjects, you should stick to one in order to get experience in it more quickly, improving your chances of landing a competitive specific position.
I'm young enough to have first started modeling in order to mod counter-strike source. For a year or two the vast majority of my output was just guns. I became a very good gun modeler. But when it came to modeling anything organic, or even something with different forms like a car, it was like starting over again.
As I got older and counter-strike lost my interest, I finally started switching up subject matter. I still made guns, and still love to, but finally I was focusing on the entire spectrum of game art instead of one sliver.
For me, the switch was incredibly enriching. Even though I was technically an experienced modeler, I encountered a million modeling problems which my experience hadn't prepared me for. Making guns poses only a certain set of problems; in focusing only on guns, I had learned how to solve those problems like a surgeon, but I hadn't been exposed to new ones in a long time.
Quoting Max Hazerman on negotiation:
"Thinking rationally about [a problem] requires that you be able to discern [it's] most important aspects, know why they are important, and know what strategies will be most effective to ... maximize your outcome."
This is expertise - the quality of getting better results more often. It requires the ability to recognize generalities between problems that are different on the surface. An expert is more likely to get good results the first time he ever tries a specific problem, because he can apply generalized solutions to generalized problems! Someone without that abstract layer of knowledge is essentially solving the problem for the very first time. And while you can't get experience modeling every type of thing on Earth, you CAN apply expertise to any modeling problem you ever encounter. Which of course is the sentiment behind the saying:
"Jack of all trades, master of none; certainly better than a master of one."
So what do you think? If you live as a specialist, do you ever expose yourself to other sets of problems in order to improve? Will you be specializing in your niche for the rest of your career? And if you're a generalist, do you feel limited (or unemployed) by a lack of significant experience in one field? Which do you think is the stronger path in the short term - when you need a job yesterday?