Second idea: you have the power and responsibility to define it for yourself, so that other people's opinion cease to matter. Once again, it will matter, because we are alive at the same time and share formative influences. But this power is an absolute one. So if I were reading someone's poem I would point out what their aesthetic is, and ask them if that's what they are going after.
Third idea: it is not a point on a line, but a spectrum of possibilities. It is not an unchanging essence, but something that can shift along this spectrum. It can expand. Poetry for me is imaginative freedom infused with awe at existence itself, so it doesn't make sense to have an aesthetic that just sits there inertly.
Fourth idea: intention. You have to mean it. You have to commit to doing it and then doing it right, and the aesthetic intention has to be palpable in the poem. I probably haven't been able to do this myself. If I had, then I would be a great poet.
My particular aesthetic is this: I start with imagism. So concrete images and a certain free verse musicality; no wasted words. That gets you about 60% of where you want to be, since that is a lot of people's implicit notion of conventionally good poetry. Then the rest of it is personality. There has to be something more, like wit, or ecstasy, an element of surprise or of the unexpected, or an enigmatic quality. My particular technique is to begin somewhere and try to make each line the logical continuation of what went before, but also surprising in some way.
So it's not surprising that one of my favorites is Joseph Ceravolo.