A good modeller gets the work done, quickly, and to the requirements necessary for the project.

But what skills one needs before approaching modelling... Absolutely zero, actually. Well, unless you count basic logic and problem solving skills, and the ability to navigate 3D space as much as is required to pan a camera around a scene. Heck, you don't need to be able to draw even if your eventual goal is hyper-realistic characters; as long as you have a good eye for shape and measurement. So it kind of depends on the person.
I know a lot of environment artists and prop artists who are modest at 2D freehand drawing, if that. Yuri Alexander, a character artist I greatly admire, just opened a thread on Polycount asking how to approach 2D drawing and painting himself, as he feels he's never really taken the time to learn it... and dang, just look at how far he's come without freehand drawing skills.

That said.

Both 2D art and 3D art are learned skills, and neither moreso than the other. You'll need a good eye for shape and measure in both, arguably this is more difficult to get a handle on in 3D. In 3D you don't have to learn things like perspective, line, form, rendering so much... but learning those is replaced by learning the ins and outs of the technical side of things instead, how to set up lights, get shaders to work, renderng, getting it to run in a game engine, UV mapping, rigging, etc.

You can pick up drawing whenever and get really good at it as long as you stick at it. Same goes for modelling, and you don't need to know 2D already to get good at 3D or vice versa. You just need to stick at it and practice smartly, setting yourself up to cover stuff you don't already know.

They're both difficult, and I firmly believe you'll be better off understanding both in the long run. Just don't try and pick up all the skills of both at the same time. :)

If you want to be a modeller, don't worry if you can't draw. Just model, you can learn composition and color theory and lighting and eventually maybe even pick up a pencil if you're interested, but you can do it on the side in your own time. It probably wont impact your models for a while yet, anyway.

tl;dr
Drawing isn't something you're born good at, it's a skill like anything else. With that in mind, so is 3D. So you can pick up whichever you're more comfortable with and focus on learning that for now; though chances are you'll at least have to get aquainted with the other one at some point. You might pick it up naturally, or you might have to work at it, but it'll pay off.

Are 3D modelers generally good free hand artists also

Yes. But I don't see why they had to be. Modeling is completely different from drawing, painting or sculpting something in real life. Modeling requires many kinds of additional skills of an artists that wishes to learn it. You could be a godlike modeler having never held a pen or paint brush.

Why in practice many 3D artists are also good with 2D and traditional art? Because they are interested in designing and recreating shapes and outside virtual environments pen and paper or sculpting are the ways to do that.

In practice for modeler it is also common to do some of the design and texturing in addition to the modeling the shape and often that is a job where artistic eye and 2D skillset becomes handy.

is modeling more something you can learn?

Yes. You can definitely learn modeling whether you can draw or not. In fact pure hard surface modeling (buildings, machines, etc) doesn't really require any freehand skills, you can just extrude the shapes using purely numerical entry or blueprints.