I would define a poetry ghetto as a poetry community that is being marginalized by another.
For example, say there is one group of poets which has decided to write about fruit. They work very hard to create all kinds of poems about oranges and tangerines, apples and plums, and they are very content writing all of these poems, critiquing each other's poems, publishing each other's poems and handing out awards for the best fruit poem of the year.
Then, there is another group of poets which has formed a group to write about fruit pies. They write about apple pies and banana creme pies and no matter how you slice it, it's a pie - sometimes concrete poetry in the shape of pie slices, sometimes pie recipes in poetic form, etc...not just pies, but fruit pies.
A few of the fruit pie writers belong to the fruit writers group and some of the fruit writers belong to the fruit pie group and then along comes a poet who likes to write about fruitcake. The fruit writers think this poet belongs with the fruit pie writers because the fruit pie writers write about fruit products instead of the fruit itself. Meanwhile, the fruit pie writers don't really think the fruitcake writer belongs with them because a fruitcake is simply not a fruit PIE.
Meanwhile, one of the fruit writers thinks there should be a fruit baking category in the annual fruit poetry awards and all hell breaks loose.
This may seem like a silly example, but it happens. For some reason, when poets form poetry communities there is a tendency to think the group's type of poetry is superior to others, when in truth it is a matter of personal taste. Since we tend to appreciate what we enjoy the most, it is an easy trap to fall into.
I'm not fond of cryptic Academic poetry, but I might try to write one sometime if I felt that style was suited to the idea I was trying to express. It would be easy for me to discount Academic poetry as completely irrelevant, yet it obviously means something to some people or they wouldn't write it, so I like to keep my mind open on the subject.
Years ago, I'm embarrassed to admit it but I didn't think much of haiku, mostly because I hadn't really experienced it yet. I kept trying to subscribe to the late Fred Raborg's sonnet journal and he kept accidentally sending me Cicada, much to my disappointment and dismay. Yet, here I am, years later, writing MOSTLY haiku, having totally fallen in love with the form.
If we are to be creative people, then I think we need to keep our minds open to new ways to experience and share our creativity. If I had never taken the time to bother to read my first haiku journal, my life would be a lot poorer for it.
And as for the poetry communities...poetry is marginalized enough in this country without us trying to marginalize each other... enough already!