Generally, staying a second year isn't a problem in terms of NBA perception.
If Mali were to come back, he'd be [presumably] the focal point of the offense, the team's leading scorer, and have every chance to show his game diversification. If he can't do the latter, that's on him. The athleticism is there, the size is there, and the shot is there. Now he just needs to put it together.
He might still be drafted in the first round, but I haven't seen anything from any reputable source outside of Ford projecting him in the first round. I've seen numerous lists / mocks that don't have him being drafted at all. Ford appears to be an outlier in his projection. I'd assumed that a dose of that reality from the NBA projection committee would be enough to convince him to come back, but it doesn't appear to be the case.