Those things could be said about Batman as well. Batman has more money and thus more gadgets and vehicles, and they have oftentimes have contrasting motivations for what they do, but they're not that different otherwise.
It's the fact that Batman exsists already ,as the main character, that ruins the idea of a Catwoman for me. She is an imitation, a copy. Just instead of a bat it's a cat. So when people compare the character of Catwoman to Batman it's not really a valid argument. Batman is the exception to the rule which is what makes him a superhero. The fact that Bruce Wayne can do all of the things that he can is truly exceptional and amazing. Throwing a Catwoman in there kinda ruins all that. And if you argue that she's not as strong or skilled as Batman then you are just re-enforcing the point that she's not all that threatning as a villian and more of a love interest. I don't hate the character and I actually liked "Batman Returns" but I just don't want to see the character again.
You do realize that the studios and the fanboys wanted the Joker and Two-Face also, don't you? Same for Scarecrow... he'd actually been in line to be a villain in the next Batman project even back when Schumacher was still involved with the Batman films. The only one that's out of place is Ra's al Ghul, and that's definitely not because he was unwanted, but because it seems like he was unexpected.
