Inconsistency is a form of complexity.
I think that's only true if you look solely at the classes and associated abilities. 1E has more potentially player-facing rules and they're inconsistent.
If you go solely with that, then it's pretty silly because you could just compare Wizards and say the 4E Wizard needed to know about 1/10th as much stuff as the 1E one, which is clearly not really true.
And if we're looking at when it was hardest to play a ranger in terms of how much you had to know rules and look things up, it's not going to 1E or 4E, it'll be 3.5E.