Just not sure why people think MJ is slow.
It's in comparison to Thomas. It's the same reason people have overstated his power running ability. If he were taking over for Nesbitt people would be worrying about his inside running, and over-hyping his speed. Athletically I see him similar to Washington and Lee. Fast enough to hit a big one if the circumstances are just right, but most of the time his big plays will be between 20 and 30 yards. Overall, better athlete than Washington, not quite as good as Lee.
What concerns me speedwise is less about speed on the plays like he scored on against VT, which was a straight follow, or on option plays. As fast as Thomas was teams still tried to force him to keep the ball. Where Thomas' big play ability came in was on broken plays where he could use his elusiveness to make things happen, and on passing situations where other teams were forced to respect his legs more and so they couldn't go as all out as they did in the past. I think that really helped our passing game under Thomas, and made our pass blocking look better than it had in the past. If teams aren't afraid of him taking off and really burning them, then they will be more likely to go full force on pass rush, which will in turn make our pass blocking harder.
IMO the state of our program means we absolutely need a QB who is elite in some area, speed, power, passing, something. Otherwise a jack of all trades will leave us where Tevin did. In good, not great years, left saying "if only x, y, or z was different".