The problem is that DC doesn't want it that way.
Books that have a general humorous overtone to them, like Harley Quinn, aren't suitable to exist in the main world of DC.
If all you want is a bit of humor featuring Diana, then just sit back and wait because you'll now have 2 books aimed squarely at you, enjoy those and leave the main one alone, thats just my advice on this.
If said readers are roughly 40-ish of age, I'd like to imagine that the biggest group is still somewhere in their 20'ties (but I dont know if thats true). Can't argue against that the current top of the pops in comics watched it, they probably did. That said, they seem to trying damn hard to make their work seem as little like that old cartoon as humanly possible.
And my argument is that the knowledge about Diana/Cheetah's rivalry is nearly forgotten because so many of those appearances are effectively hidden away in obscure works that most people never see.
But like I said, notice how little the works of these creators resemble the old cartoon.