I'm sure Whedon knew about Simon, but he had 2 hours and he's not going to waste that setting up Simon. Originally he wanted Janet van Dyne, played by Morena Baccarin, to be his Wasp in the movie but that was let go once filming began. And it's the MCU things aren't the same, part of what changed Hank Pym not being there, if they even wanted him there's as because Edgar Wright had dibs on him for Ant-man. Except Wanda is very close to the twins in the comics, she's routinely there for them as a gust star in Avengers comics and recently Billy's husband defended her against Krkaao via diplomat in SWORD. Read Ewing's New Avengers, I think in her recent solo she helped Billy plan his wedding.
Wrong, men write romance in romance books. They're rare and many use female aliases because people are turned off by men writing those books. Nakia was incredible in Black panther, I could see why he'd want her to be his queen and they had chemistry together. The Bruce/Nat romance was a dud, but the movie behind the scenes was a train wreck. Whedon was burnt out for working on the MCU for years between Avengers films. Just because Vision didn't rescue Wanda himself didn't mean he didn't care about her, clearly he does but it's Cap's film so he gets that task. Their relationship is mostly done off-screen, which is why they're much closer together by Infinite War. It's hardly been a fast relationship, it's been built up over multiple films with ups and downs and neither got them are allowed to be centre stage. Was their relationship rushed in the comics? They were together for years on again and off again, got married, had children. Most super-heroes don't have relationships that last that long. Writers had to to absurd lengths to break them apart. Lois Lane barely started dating Clark in Man of Steel, they just met over a couple days in that movie. Just because many male writers don't do good romance don't write off the entire gender, and there are eight writers on Wanda Vision, what's difficult is to find who they are so I don't know if any are men. The other shows will have romance, as well, and you can bet they hired male writers for those shows. I don't expect much romance form Falcon and Winter Solider but Ms. Marvel. Yes. She-Hulk? Yes. Moon Knight? Yes.