TwoSix
Everyone's literal second-favorite poster
I think there's some tension here between "What's best for an individual game" and "What's best for the game line." For an individual game, reskinning is fine and dandy and should be encouraged, there's nothing wrong with reskinning a sorcerer, a wizard, or a cleric as a psion, depending on how the player wants to express the powers.
D&D as a game line, though, has depended on the idea that discrete mechanical elements represent different concepts within the game fiction, even when that isn't fully coherent. Psionics has always been represented in D&D as "not spells" (which indicates a fictional relationship between arcane and divine magic that also strikes me as incoherent, but ¯\(ツ)/¯ ), so it's not surprising that suddenly relating psionics to spells gets some pushback from those who are more traditionalist in their approach.
D&D as a game line, though, has depended on the idea that discrete mechanical elements represent different concepts within the game fiction, even when that isn't fully coherent. Psionics has always been represented in D&D as "not spells" (which indicates a fictional relationship between arcane and divine magic that also strikes me as incoherent, but ¯\(ツ)/¯ ), so it's not surprising that suddenly relating psionics to spells gets some pushback from those who are more traditionalist in their approach.