I actually think who coaches a young qb is important. In the long term they teach them the thought process, how to read a defense, see disguise, and drill in the correct response to what they see to imprint quick decision making by it being a natural response rather than a thought process.
In the short term some OCs can design game plans to hide a QBs weaknesses (McD with Mac) but before long that is exposed.
For example Brady was far ahead of other QBs with the intellectual part and the speed of processing. A “genius” in those areas can help young QBs become stronger at it, and ultimately it’s the most valuable trait.
On the other hand you have a guy like Gruden who takes the timing of the WCO to an extreme and teaches his QBs to always take the quick pass and they rarely learn how to read down the field opportunities.