If we consider what is really helpful for a person, it could be a number of things. I have certainly not experienced it to be that single decicive conversation with an all enlightened teacher. We could learn from our daily life, by observing nature, a kalyanamitta, or our mistakes. As long as teachers don’t have high expectations from their life-changing answers, they will be ok. 
. I would go with thinking of any answers as suggestions, and if the meditator wants to put them into practice, it will be upto them, if and when possible. Life is complicated so I can fully see someone asking a questions when inspired by a dhamma talk but finding it difficult to carry it out.
In depth assessments of personality would be nice, but that is no guarantee that it will be effective though. Having lived with someone it is easier to give much more applicable advice. But we do not know by what hindrance they have not figured it out themselves and whether bringing something to their notice is an adequate intervention. Also, some people aren’t able to articulate their emotions (‘alexithymia’) so many not be able to report what their problem is to a teacher. As long as such people are engaged with group of kalyanamittas it maybe helpful (though they may not be able to recount how it helped).
Overall, I think D&D and SC is a generally pretty positive place to be at, comparatively. It is not Utopia (‘sukkah thinking’) but realistic as human interactions go. I think it is in this ‘human realm’ where our practice will happen- within the interactions of this forum and not in a ‘deva forum’ where everyone is perfect! I’m saying, our interactions on the forum IS the practice and is conducive to it as it has a bit of negative and positive. I personally find interacting with everybody keeps my brain thinking about the dhamma and helps bring those brain connections in line with the dhamma. This is what being with kalyanamittas is about- its about the dhamma. Even discussing the suttas is beneficial, even if it is obscure pali.
with metta
Mat
ps- lot more to practice than meditation.