I think the biggest problem for Google and Amazon is conceptual - like, who is it for? You can definitely find people that it suits, but can you find enough that it is going to be a notable and profitable service? Everyone has a phone and everyone has their phone on them all day long, so the only games that the cloud service can meaningfully entice you with are ones that feasibly cannot exist on a phone. And who is thirsty for those types of games? People who already play those types of games, largely. And these people typically already own consoles. Maybe you can snag a few lapsed hardcore gamers here and there, but that feels like a rounding error in the margins of the market.
You can posit a future where the console is no longer required as an entry point, which is what Stadia and Luna are attempting to be. No hardware required, just get up and go! But if you're competing with Microsoft, Sony and Nintendo to attract their customers, and they can simply turn around and offer cloud services with full integration with their existing (massive) ecosystem of games and exclusive content, I think that's a daunting prospect and one that I cannot see being a winner. When we heard about Google getting spooked by Microsoft buying Bethesda, I can understand why, because Cloud isn't actually an entirely seperate blue ocean for gaming like they might have sometimes envisioned it as being 8 years ago on a drawing board when these big ideas were getting started internally. It's a very, very red ocean, where they need to go head to head with Microsoft and Sony (and to some extent Nintendo) to try and attract their customers.
The tech for Stadia is not something I'll critique, it's better than what Microsoft and Sony have, but I don't think it has much life in it as a platform. And the advantages of ecosystem integration from them are kind of killer when comparing business models, imo.