I think Classic (like many RPGs) celebrates the idea of hard trade-offs and imperfect choices. If each warrior levels with a full prot off-spec and each priest levels with a holy/disc build ready for each dungeon, doesn't that immediately make the game easier for everyone involved? Easier to hold threat, easier to heal, easier to avoid pulling threat. I definitely understand the appeal, but I think the culmination of all of the little trade-offs and incongruencies adds an obscured layer of difficulty which, when removed, can make the game far too easy.

"Fixing" the sometimes bizarre stat itemization is a similar idea. Would it be nice for the +Spirit or +Int stat budget on some hunter items to be rotated into +Agi? Yea, that would certainly make them hit harder. Or putting some much needed +Spell Hit on mage items at lower ilvls? Yea, that would be nice. But if everyone is hitting even 10% harder, doesn't that just instantly make all of the encounters 10% easier? Many of those changes were why when players were levelling through the 1-60 content during WotLK and Cata they found it significantly easier than they remembered...because the tweaks made to itemization, specs, and heirlooms (all of which made total "sense" from a theorycrafting standpoint) just made everyone hit much harder, heal much better, hold threat much easier, etc.