I heard it said (I’m sorry, I can’t remember where) that amateurs are interested in cameras, enthusiasts in lenses and photographers in light. It makes a nice pithy aphorism but does nobody any favours.
So ‘real photographers’ can’t be interested in cameras? And anyone who knows how their camera works can’t be a photographer? I think the phrase we need here is bollocks. I’ve argued elsewhere that technical aptitude is on a scale and that we should ideally try to combine an interest in both outcomes and methods.
What is more useful to think about is not camera, lens or light, but camera, lens and light. They are three variables that can be combined to make a result. You could think of them as another exposure triangle.
The camera makes the picture possible and dictates the type of picture you can make. I wouldn’t use a large format camera to shoot sports or action, for example. I know it’s been done, but so has Morris Dancing. There are better ways, unless the difficulty is part of the intended process. So the camera should be selected according to the job it has to do.

The lens makes the camera work and controls the type of picture. It lets you compress everything into the frame or isolate a detail. Without a lens of some kind you can’t form a picture. That light won’t just focus itself, you know. So the lens should be selected to frame the subject and to achieve an effect in the image.

And neither the camera nor the lens have any point without some light. But I think it’s useful to also distinguish light as the subject from a subject which is lit. It’s possible to make pictures where the subject or purpose is the beauty and placement of the light. It’s also possible to make pictures where the purpose is the subject and the light serves to make the subject visible – think of photojournalism.

Perhaps the ideal, and the art, is to be able to see and combine a good subject with the best lighting. Then to use the best lens to render the subject and lighting in the way you want. Then to use a camera that allows you to capture what you intended.
So I don’t think the camera, lens, light axes are exclusive: you need to combine them. But perhaps what the original claim really means, and which I believe, is that your picture starts with a lit subject. You then work back to the equipment and settings needed to capture what you saw. If you start at the other end, say with the camera, then you are led to find things to put in front of it. I think this is why I have some cameras and lenses I seldom use. Taking a camera for a walk feels boring and restrictive. What I prefer is to go for a walk and take a camera plus lens that suits the conditions, the things I might find and the type of pictures I have in mind. But, saying that, I have used the constraint of a particular combination of camera and lens as a method of getting out of a rut and trying something new. It was never meant to be the starting point though, just a way of taking constraints to an extreme. It does make the point though, that starting with the camera is the wrong way round.
Fiat lux, as the Romans used to say.