Intangible hockey laws dictate that, save for some generational exceptions, defencemen take longer to develop than forwards.
Elite scorers establish themselves in their early-20s and ride their primes until they putter out by 35. But defencemen need to hone their craft for years, smooth over scrunched bits in the tapestries of their game. Scoring goals is an innate talent; preventing them is a learned and calculated skill.
Blossoming as a premier NHL defenceman demands patience, poise, and a knack for trial and error. And the final decade of steadfast and masterful defence usually pays for the first handful of years as an apprentice anyways.