One of the problems that photographers have to deal with is that, unlike other art forms, basic photography is pretty easy. To reach a level basic competence (by which I mean, your work has some commercial or artistic value) in other art forms, like painting, music, dance or architecture, typically takes years. A few hard weeks of work in photography will will generally get you to a level of competence that could even generate sales, if you pick the right commercial venue. IMHO, this tends to attract people who really don't care to work very hard at an art form, but yearn to be some kind of an artist...so they pick up a camera, and they eventually begin searching for things like style.
Again, this is my opinion, but I think that most serious artists or even businesslike commercial people tend to do things the other way around: that is, they have an interest, and then they adopt an art form that will capture that interest. That combination -- an interest that can be captured by a particular mechanism (dance, drawing, photography) leads almost automatically to what we call style. That doesn't mean that you always shoot the same thing, because you may be interested in more than one thing. But even in that case, in pursuing your first interest, you probably gravitated toward a particular "look" simply because you like it and think it's effective, and so you carry that over into other subjects. Robert Mapplethorpe was interested in sex, portraits, celebrities and flowers, but the "look" is very similar across all those categories, because he found that look appealing and to most accurately or effectively represent the way he saw things.
The push to develop a 'style," I think, is a problem mostly for those people who really aren't deeply interested in anything in particular (or at least, nothing in particular that can be photographed.) Although some people might not believe this (especially if you ARE an artist) I observed over quite an extensive career of reporting that many, many people really aren't deeply interested in much -- often not even deeply interested even in their families or in their jobs. That doesn't necessarily mean they're stupid, it just means that they aren't deeply interested in very much; I once briefly dated a woman who was interested in going to parties -- not documenting them, or commenting on them, but just being there. Having fun. She didn't even have a stereo, or read. She wasn't stupid, she just wasn't interested in much. If you look at all the millions of hours frittered away on Facebook, Twitter, messaging, browsing the net, etc., you realize that many people are quite content to eat, sleep, drink and message. If one of those people begins to feel a vague yearning to become an artist -- usually because he/she likes the idea, rather than the reality -- then photography is a natural choice, because you get to carry around some neat equipment and because, basically, it just isn't very hard. Until, of course, somebody tells you that you need a "style." Then, if you're not interested in much, you're sort of stuck. You wander around, doing a little street here, a landscape there, a portrait of friends, some snapshots of family...there's no style because you're just going through the motions of photography. If you get desperate enough -- photography equipment isn't cheap -- you start looking for articles that tell you how to develop a style.
In my opinion (I say again) if you really want to develop style, you should put the camera down, and spend some serious time thinking about what you're deeply interested in. If there is something, go shoot that. If the honest answer is "not too much," then maybe you should consider dropping photography for a faster internet connection and maybe a subscription to Netflix.
One subject matter, of course, is almost always of interest -- which is why we've seen the spectacular rise of the selfie. Not that anyone else wants to look at them.