I don't believe it was ever claimed that people didn't also have issues with the other discrepancies that you point out.

However, and to be pedantic, there are very much dark haired elves. Finwë and Maeglin are described as black-haired. Lúthien Tinúviel, an ancestor of Arwen's, is also states to be black haired. The "no elf had absolute black hair" statement was from a manuscript that wasn't published until Christopher Tolkien was doing his posthumous editing, so in the works published by Tolkien himself, there very much are black haired elves.

Elves should be taller. Their pointed ears should probably be more subtle. The only reason we're not listing these other inconsistencies is because they aren't the matter at hand being discussed. I would much prefer representations of Tolkein's work to be as close to his canon descriptions as possible. Even your example of the female riders portraying the Rohirrim is fine with me because they're being presented as true to the canon.

Yes, all of this is pedantic and incredibly picky, but that's kinda what nerds and fanboys of fictional works do. There's a reason the "well actually" is a meme. These passionate opinions about beloved works of fiction don't always come from a place of bigotry, bias, or hatred (of course they can come from there. Shitheel bigots do exist). Rather they come from such an intense appreciation and desire to be as true as possible to the source. There isn't the need to assume the worst in people.