you are discounting the fact that Williams., Mcdaniels and Nix have been in college for 6 years due to all the transfers they had. That's 2-3 more years of getting to work on your footwork, reading defenses, and throws to gain accuracy. Maye had just 3 years of college, while the others double that experience.
Jiust about every one of the great QB since the turn of the century didn[t start right out of the gate, Brady, Mahomes, Rodgers, etc all spent at least one year watching and learning the NFL game. Thats not to say that those rookies' starters won't eventually be good QB's, BUT you can see that thus far, all 3 are struggling with areas of the NFL's defenses. PLUS you have the cautionary tale of Bryce Young's fall from grace. QB is the toughest position in professional team sports to develop since it is so much more than just having the athletic gifts.