Bedrockgames
I post in the voice of Christopher Walken
In D&D generally, the change to fiction players control is what their character does. Supposing one is satisfied with that, then MMI doesn't arise from how the results of that are narrated. Supposing one isn't satisfied with that, this happy picture changes.
but again this is a lot less I think to do with something called MMI, and a lot more to do with play style and preferences. Some people like RPGs where you change things by acting through your character and what your character does, some people like having more external control over the things. Some people like a blend. And some people don't care about this concern one way or another (they just don't even think about when they are playing).
One thing I don't get about these discussions is why people care so intensely about it anymore. I don't play 5E. It doesn't hit all the buttons for me in terms of what I want out of D&D. But I don't feel the need to attach some negative label to things it is doing. It is just clearly not an edition designed for a GM or player with my tastes in mind, and that is perfectly okay. Many people I know love 5E, many times because it has the very things in it I don't like. There are just so many options now. It sounds like most of the posters who have issues with 5E have found games that meet all the criteria they are concerned about. I think in these circumstances people are a lot better off promoting the games they like, then ripping down a popular system because it isn't enough like those games or isn't enough like a previous edition of D&D that they preferred. I just don't think you are going to persuade people with the MMI argument because it basically is a 'your tastes are bad' argument. It is like the magic tea party debate or like the narrative games 'aren't RPGs' debate. It positions a system or style of play as inferior and flawed, using label that is powerful (again Mother May I is a child's game where people have zero control over their own bodies, it isn't a flattering term, and it is a label people would want to repel off them because it is emotionally charged).