Of course Willis looked amazing at his Pro Day, lots of guys do. He looked amazing in a highly controlled environment. An environment with no defensive hands in his face, no one trying to bring him down to the ground, no having to look off multiple receivers downfield, no one playing at NFL game speed, and no having to change the play at the line. He had a 61% completion rate in college, was never asked to do anything complex as far as offensive playcalling goes, consistently threw the ball to the first read, locks onto a target and doesn't go through progressions, and hasn't shown a high football IQ where he can make split second adjustments and call the right audible at the line. I don't know what his football IQ is, he could be a Russell Wilson or Payton Manning for all I know, but I suspect not based on his colligate performance. The changes and "audibles" he does make are largely to get himself out of a tight situation with his athleticism and scramble his way out of it. As other mobile QBs have proven, you can't just scramble your way out of every situation in the NFL. These are not audibles where he's reading the defense, deciphering the right play to call and making the adjustment at the line with his teammates. If you could just plug in an athletic, mobile QB then over the years the Tyrod Taylor's, Mike Vick's, Vince Young's, Mike McMahon's and Johnny Manziel's of the world would be MVPs season after season.
I love the physical tools, I love the cannon of an arm, I love the freakish athleticism, I love that he looked amazing at his Pro Day. I suspect all that falls apart during an actual NFL game and what you're left with is a mobile QB with a big arm, subpar decision making and average at best accuracy. Your left with a stronger armed Jalen Hurts or Tyrod Taylor.