Generative AIs are cool tools people can use to make things but they're not magic. Once you ask for things outside of their training set you get really weird results. Even with a lot of fine tuning (LoRAs etc) results can be hit or miss for any given prompt. They're also not very consistent so which means series of clips are incongruent or just mismatched.
That doesn't mean generative AIs aren't going to be useful and won't impact film making. You're not necessarily going to be able to ask ChatGPT to "write me an Oscar winning screenplay" but you can certainly use one to punch up dialog or help with story boarding.
I think he's right on that visual effects people will be hard hit because there's going to be a lot less jobs for mundane tasks like cutting out an errant boom mic or Starbucks cup in a shot. I'd extend that to other "effects" jobs like ADR since can AI can fix a flubbed line in an otherwise good take.