While it may be possible for one single quality to save or destroy a poem, there are usually several factors that can be used in judging one poem to be better or worse than another.

The amateur bad poet tends to use longer and more unusual words as well as longer and more unusual sentence structures, under the mistaken assumptions that greater detail equals greater precision and that greater volume equals greater content.

The expert bad poet uses shorter, more common words and shorter, simpler sentence structures under the correct assumption this will make it easier to read and to understand.

Thus, when we read a bad poem by a professional bad poet, it is only clearer to us that the poem has nothing of value to say.

It's the difference between the monkey that throws shit at the wall and the monkey who throws shit at the ceiling.
The raw aesthetic of first monkey's work is more conspicuous, but the ultimate effect of the second monkey's work is more compelling.

>How do you define bad poetry?

We don't define it, we embrace it. And alts too. We embrace those also.

>Can a poet who writes bad poetry write a "good" poem?

Can an alt that writes a bad question write a "good" question?