It certainly could be that despite the appearances being better in say, 1950-2000, that actual corruption was equal or worse, and most of it went undetected and unpunished!
But my take is that it wasn't as bad, because shame used to exist. A politician would "resign in disgrace" when caught in a medium-to-large scandal (even one that seemed technically irrelevant to their responsibilities, like 'sex scandals'). And he would stay out of public life thereafter, out of shame, knowing he couldn't run for office again and win because of their shameful past. Compare Richard Nixon vs. Bill Clinton.
That's what changed. Now it doesn't matter how shameful and corrupt your conduct was, you just either deny or answer with whataboutism towards the other party's worst sins, and carry on, and for some reason voters are consistently fine with this!