Historically the process of mastery relied on an apprentice-master model based on rigorous emulation, with the apprentice repeatedly fumbling through tasks until basic skills were mastered.
Only then would an apprentice move onto more intricate elements of the trade.
Following this process the apprentice would eventually be able to produce a "masterpiece", that is indistinguishable from the master's work.
This process used key pillars of learning necessary for rapid and effective progress. Clear goals, sustained supervision, expert critique, daily deliberate practice, and adapting lesson difficulty.
Today mastery of a skill is largely acquired through instruction from sources such as JPA, but the key pillars of learning must still be present if one ever hopes to achieve mastery.
Many photography schools teach using unstructured, informal, disjointed, and in-field crash course style training. This training style is often reactively driven by student questions. This approach usually only provides a student with a vague familiarity of key concepts and does not meet the required pillars for true mastery.