I'd be a fool to shrug off the relative youth of the coaching staff, especially given the inexperience of our head coach.
Running an organization is no joke. It requires more than scheming and playcalling - it requires the soft skills to successfully manage individuals, workloads, and personalities as well as effective delegation. These are things that generally come with experience.
With that said, I'd also be foolish to write them off. I think we've got a few steady hands to lean on, especially that of Leslie Frazier (who was our fall back option while we pursued Pete, IIRC) who I expect to handle a lot of traditional head coach duties (probably including game management) while Macdonald calls the defense for now.
These guys are going to have to learn how to work together. They haven't been around the block enough times to seamlessly transition. There will be hiccups. There will also be the vigor and energy associated with that youth.
It's year 1. If the growing pains are too much, that can theoretically be amended going into year 2.