I think you have to start by making a fundamental distinction between good and conformant. Obeying a set of rules makes something conformant but it does not make make it good. A Lada is conformant to the characteristics of a sedan, but it is not a good car.
This is not to say that there is no relationship between being conformant and being good. Any desirable quality that is measurable can be made into a requirement, ensuring that anything that is conformant is, to that extent at least, good.
But there are many things we value that we can't measure. What makes poetry good cannot (yet, at least) be reduced to a specification. A perfectly conformant haiku can be a bad poem. For that matter, a non-conformant haiku can be a great poem.
What makes a poem good? I think I am consistent with a pretty broad and longstanding tradition when I say that it comes down to insight -- what the poet sees -- and expression -- how they use words to cause us see what they have seen.
Exactly how or why conformance to particular constraints such a meter, subject, or form -- the haiku form or the sonnet form -- should help poets do this (when it seems that the additional requirement should only hinder) is more than I know, and perhaps the modernist would dispute that it helps at all. But there seems to be a pretty long and strong tradition that suggests that it does.
Either way, these constraints define conformance, not quality. A conformant example of a haiku or a sonnet obeys the applicable set of constraints. A good haiku or a good sonnet makes us see the world more acutely. To be good you need insight and a facility with expression that goes well beyond conformance to the form.
I'm not sure that insight and expression can be taught (they may, perhaps, be encouraged, mentored, or even modeled). I'm pretty sure though that neither can be broken down to a the kind of concrete advice that is suitable to an SE answer. Various individual techniques of expression, certainly, but not the whole art of it.
