@ph0rk
I think, perhaps, that the problem may lie in the way you view the relationship between the wizard and their power? That is, it seems to me that you start off with the perspective, "A Wizard desires power, and thus pursues Wizardly ways because those are an
excellent investment."
Would you describe any of your Wizards as the kind of people who investigate puzzles or enigmas
solely because they are unsolved, without any consideration for the power or influence they might gain from solving them? If not, then perhaps that's an anodyne to this seemingly-inevitable march toward selfish lowercase-e evil. Pursuit of knowledge and magic, not because these things grant
power, but because it's literally just a surge of
sheer joy to have an epiphany or craft a new spell.
Part of why I say this is, you've noted that other spellcasters don't experience this process, making particular note of Sorcerers. A Sorcerer never
sought out their powers in the first place (or, at least, the "expected" way of becoming one is a family-tree surprise), these powers just
happened to them. As a result, while they might choose to explore those powers, their behavior is not in principle
motivated by those powers. Compound this with the examples you already gave (they're social butterflies, thus inclining you to think socially; they're spell-limited, turning you away from pursuit of elaborate efforts and spellbook-filling), particularly given your statement that Bards could go in a similar direction due to their ability to pick up spells from other lists, and I think there's a pretty good case to be made for this. You see Wizards as, more or less, dragons of knowledge, already isolated from society due to their nerdy pursuits and ever-more-isolated due to their need to (literally)
know it all.
I think it might be an interesting challenge for you to play a much more happy-go-lucky, "eternally wowed by the mysteries of the universe" type Wizard, the type that only researches a new spell because it tickles her fancy, or who dives deep into investigating the potential uses of seemingly-useless combinations. This contrasts very heavily from your extremely practically-rooted mindset you've described, where the thing that doesn't change is "I must acquire knowledge so I can acquire power, therefore I must acquire
as much knowledge as possible so I can acquire as much
power as possible."
If power never becomes a motive because "eh, power, who needs it? I just like looking for answers to weird questions," you might find yourself following a different track.