@Ian's point was to compare Mac to a "great" QB, I'm not sure which "great" QB drafted in the last decade that started week 1 (or around week 1) as a rookie you'd want to use as a comparison. Looking them over, the best I can really find are Andrew Luck in 2012 and Deshaun Watson in 2017. Besides them, the best you can do is compare him to other QBs who were drafted in recent years and
could be great but the jury's still out (Baker Mayfield, Josh Allen, Kyler Murray, Joe Burrow, Justin Herbert). And then, obviously, you have the easy comparisons of Trevor Lawrence and Zach Wilson this year.