If you search for images of "self-expression" on Google, you'll get a collage of photos that are going to look like this. I could think of no better way of showing exactly what I mean when I talk about--and criticize--self-expression.
The irony here is that in all of this so-called self-expression, the results are almost universally identical. It's all a miss-mash, with lots of color. What this suggests is that everyone's self-expression is like everyone else's self-expression. And what does that mean for either the self or it's expression? It means you're just like everyone else if this is what self-expression looks like. And that's precisely the problem with self-expression as art. It isn't art. It isn't even, as one of the pictures suggests, self-love. Love is always of a particular thing or person, and if there's anything this example of self-expression is not, it's particular.
With that kind of introduction, it's probably not surprising that I would say that perhaps the worst thing that ever happened to poetry was the emergence of the cult of self-expression. Although one can find this cult at play in the other arts, it seems to have hit poetry the hardest, and ruined several generations of poets.
Of course, the opposite end of this is the kind of academic poetry that is only produced in university English departments, only read by other academic poets, and only commented upon by academics trying to get scholarly papers published--a task made easier when one is dealing with "difficult" poetry.
Karl Popper once defined true artists as those who are attempting to work out artistic ideas and problems--which is to say, those related to myth, structures, traditions, etc., in light of changing social conditions in which the artists are working. It is an evolutionary process, and it always is in touch with what came before it.
Certainly, one could argue that contemporary academic poetry is doing precisely that. However, the avant-garde, as the academic poets fancy themselves to be, pride themselves in making radical breaks with the past. This is, of course, unlikely to be literally true, in much the same way that the surrealists never really allowed their "automatic writing" to go unaltered (a simple example: what are "automatic" line-breaks?).
The real problem with what I'm calling academic poetry is that it, much like academic art in general, is created after the "artist's statement" is created--even if it's created only in the artist's head. This is in part the fault of most of our artists having become academic artists because they first passed through university classes.
The funny thing, though, is that the undergrad poetry writing classes all tend to encourage "self-expression." The professors don't want you to stifle your self-expression by using form or any kind of constraint. In the meantime, many of them are writing poetry most of their students wouldn't understand. As the creative writers move into grad school, those who are writing more academic poetry tend to get more encouragement while the self-expression poets get left by the wayside.
One of the main problems with self-expression poetry--and the reason it gets left by the wayside, and why most such poets eventually stop writing--is that there is really only so much self to express. Most people are like most other people. And really, almost nobody has anything particularly interesting to say--and if you do have something interesting to say, it's likely going to be said in a few poems, a few short stories. And then, you'll be done.
While the academic poets do seemingly at least try to work out some kind of artistic problem, the problem they have is that they don't produce anything anyone wants to read. Not even the academics writing scholarly papers on today's academic art aren't interested in it. They just need to publish, and it's easier to publish something on a work that is contemporary and difficult and, therefore, hasn't been touched by anyone else, than it is to try to say something new about Shakespeare's sonnets, for example.
This would seem to put us in a quandary. If self-expression doesn't create lasting art or artists, and academic poetry isn't going to be read by anyone, when where does that leave us?
Fortunately, these are not the only options.
Another way forward is to first abandon self-expression as self-centered, narcissistic, and indulgent; then, we need to familiarize ourselves with the global traditions, become global classicists, and familiarize ourselves with the world's myths, poetic structures, and forms. We must keep in mind, though, that postmodern academic art is now part of that tradition. It was at least participating in the art of poetry in the Popperian sense, even if it sent itself into abject unpopularity due to the direction the poets went with it. However, to move forward, we have to bring things back to foundations, writing works that people would actually want to read, because they tap into the brain's love or rhythms, sounds/music, and archetypal imagery. Challenge, yes--but do so from a place of familiarity.
None of this is to say that you will no longer appear in your poetry. How is that even possible? Your poetry is necessarily going to reflect your world view, your attitudes, your fundamental beliefs, your passions, and so on. How can they not? Just don't make the mistake of either thinking that your art is all about you, and do not think your poetry is going to change the world because you're undermining capitalism by subverting grammar or some such nonsense. You're not. That's not how poetry works. Its power is elsewhere.
Remember, the Muses are the daughters of memory and inspiration, of what your brain retained of external knowledge, and the way your brain unconsciously processed that knowledge through your emotions. The "you," the "self" that is being expressed is in that unconscious processing leading to inspiration. It's not vomiting your emotions onto the page. Indeed, self-expression is the subversion of poetry to your emotions, ideas, and thoughts rather than entering into a dialogue with the world's other poets, and your audience. You have to love the art enough that you want to serve it rather than make it serve you. And that means entering into the global history of poetry, bringing not just yourself, but your contemporary society, culture, and knowledge with you.