Ok fine. So what is the criteria? Let's see what wikipedia says:
I don't think GoW, Uncharted or any RPG qualifies as a casual game, based on the above. RPGs are generally the preserve of hobbyist gamers due to complexity and time investment alone, before we add difficulty. My boomer dad could figure out how to play Bejewelled, Candy Crush, Match 3 etc., but would be overwhelmed and struggle to pick up an RPG like GoW.
So if it's not casual, is it at least easy for an experienced RPG gamer? That totally depends on what difficulty level you pick. Is it for very hardcore gamers only? No, because it has difficulty settings that can be tuned down to quite low. It's not DS3 or Sekiro. If your only available difficulty levels were the top 2 ("Give me a challenge" and "Give me God of War") then I would say yes, even many hobbyist gamers would struggle to complete it. But that's not the case.
EDIT: It's a pet hate of mine when people describe games with difficulty settings as easy or too easy, because they play it on easy mode. Especially when the game has difficulty levels hard enough to make you want to break your keyboard/controller.