Chasing casuals isn't a bad idea. Nintendo does it Pokémon and Animal crossing.

Stadia relied on casuals who happen to have a stable fiber optic cable internet connection.

I disagree with this use of metric completely. I game a lot, and I own multiple devices on your list above yet subscribe to 0 of the subreddits. People subscribe to the subreddits of _games_. You didn't even count /r/nintendo instead. If anything, I think the fact that these subreddits have so many people is actually a point against what you're arguing about the size of the casual market. I do agree with you on the larger point though, stadia had no product/market fit