If he wasn't John Landis' son he'd probably be another middling tier screenwriter doing projects barely anyone cares about. Oh wait, that's exactly what he is.
I'm not sure where people get the idea that his father's name has brought him "success" unless you count success as "continues working". Like, a resume that includes Chronicle, Victor Frankenstein, American Ultra, that's what we're upset about? If not for Landis' force of personality he could just as easily be the guy who writes The Accountant, or Earth to Echo, or any of the other dozens of mediocre movies that Hollywood puts out every year
I just can't get upset about Landis. He's a loud guy on the internet in an era where everyone is loud on the internet. He's a working screenwriter who continues to get work, but there are a lot of those. His dad's connections helped him, but its not like they helped him work on the next Spielberg or Nolan movie or anything