My portrayal of Mikal is that he's a bit prideful about his obedience to God/his duties so he continues to speak with a higher recipient in mind. He also prioritises his dealings with celestial beings and diabolical beings over humans. When he is constantly asking God to forgive humanity he is dealing with God, not humanity. When he is battling with Iblis he is dealing with Iblis, not humanity.
He enjoys humanity as a concept but he has no human friends thus far, apart from his host's ex partner (who is weary of him) and their infant daughter (who cannot speak.)
He even refuses to access his host's previous memories whilst his siblings will engage in a more symbiotic relationship (metaphor for self awareness, learning from previous mistakes, actions, etc.) This is due to the resentment he feels for having to inhabit a body that is not operating at full capacity, and experiences substance withdrawal, dopamine dysregulation, has worms, is shooed out of nice places, etc. He does not wish to learn about the minutia of human life, which is to his own detriment as well as the mission's.
This is why he speaks how you'd expect Jibreel and Israfil to speak and why Jibreel and Israfil (who have had more dealings with humanity and are curious about the physical world) sprinkle "hey" and "yikes" into their vocab