I'm... afraid I'd see it differently.
The Potter-verse is a fantasy setting, albeit one that is hidden in an IRL 1980s/1990s (etc.) world. What's one of the most common bits about fantasy? "There was a golden age." Frequently when all the best magic, spells and items, was created. The modern day is (just) using crumbs of 'ancient knowledge'.
An interesting bit about the Potter-verse? People may act as if the above is true, rely on 'ancient works of knowledge', but, there's people... doing new stuff, research. And the mundane world, which the traditionalists would love to ignore? Can't be, as that's where new magicals keep getting found.
The Potter-verse is a fantasy world of wonder, having a collision with the rapidly changing world of 20thC mundane Britain.
Humans, mundane or magical, don't like unexpected change. Even the innovators, they want a 'stable place to stand', while they make change. So, conservatism, "I want the stable world of my youth" (which, BTW, never existed - memory is funny like that).
So, "Don't rock the boat", "Things aren't perfect, but they could be a lot worse". The magical world isn't, particularly, corrupt, it's doing the "bury head in sand" bit, while hoping things aren't falling apart. Pity, they've been 'falling apart' for a century or three now...
Not a matter of 'Light' vs. 'Dark'. More
Future Shock...
For, extra, extra, super, fun? This mess just got Skitter'd.