Well, Dart is going to spend his rookie year on the bench behind two experienced veterans. A year to learn, watch film of his actual offense, and run it in practice (albeit with probably limited reps). That's the ideal for any rookie with RARE exceptions.
Sanders is going to be competing in training camp with Flacco, Pickett and fellow draftee Dillon Gabriel. According to Deion, Shedeur is the best QB on their roster. I think his career depends on whether the coaching staff agrees with that assessment.