GeForce Now isn't a failure per-se... but it's a weird and complicated Licensing situation.
Not that I care much as you can only use GeForce Now via the GeForce Experience App that in turn is only available with GeForce Hardware.
I have none, so it's hard to care.
Stadia on the other hand is an abject failure.
Likely because the Latency wasn't great... the Interface is a bit clunky... you REQUIRE an Android (Phone or Firestick) Device in order to actually use the service, before any subscriptions and the subscription itself doesn't cover all the games... with most being available as Purchasable Options (and at Full Retail Price).
It's frankly too expensive, too exclusive and not overall a good experience.
The irony being that Microsoft use the EXACT same infrastructure (from AMD) for XCloud (which is now part of Game Pass)... and whatever Microsoft did to the infrastructure for the actual networking., it has better latency, fully supports 4K/HDR on all games even without High-End Internet being a requirement; and all the games on Game Pass are supported (174 at present) and part of the subscription charge.
Now in fairness I've not really used it outside of the Insider Program, while I was helping test it... as frankly I don't see the need / point.
It makes sense on Mobile Devices (Tablet, Phone) to be able to play High-End Games that it'd never be able to run; esp. my own which barely plays most mobile games given it's weak Mediatek CPU/GPU Combo... but then most games suck on such a small screen; being difficult to impossible to really enjoy ... and on-the-go via 3G/4G/5G., it's not ideal as Gaming / Streaming is a serious bandwidth hog with most places you'd want to play (Train / Plain for example) not exactly having great service coverage.
PlayStation Now is in a similar situation., it works fine and has an excellent library of games; but again... it solves a problem that no one really had, and doesn't solve the technical issues with said problem.
People oft hype over Cloud Gaming as the Future., but most have never used it... or if they have rarely go back to using it.
The reality is... it isn't good enough, and frankly can never be good enough to replace Physical Hardware; and as Physical Hardware is always getting faster, smaller and better.
I mean if I'm on the Train or a Flight., I have my Switch with a USB-C Charger Kit and Battery Pack.
It's just a BETTER solution.
I'd love to see an Xbox Portable., or a PS Vita 3... as competition to said Console; taking a similar "Home" and "Travel" approach to a Console; but neither Microsoft or Sony really take the Portable / Low-End Market _as_ seriously as they should.
I mean look at the size of the Xbox Series S., it's a powerful console but not much larger than the Switch overall... it likely could be engineered to fill a similar Portable / Low-End Gaming Role.
Sony also need to get out of their own arrogance to always be pushing Hardware Boundaries... I mean a major killer of the Vita was the price of the Device given it's limited scope and lack of Software; again Sony could have a similar "PS4 Pro" Performance Semi-Portable with a similar footprint.
They would be excellent devices; and if you ask me... THAT is more the future of Gaming, the idea of the Multi-Purpose Gaming Device.
It's the major leap that Mobile Phones made., to become "Smart" Phone; there's little smart about them, they just expanded what they could do into the Software and more General Purpose Design.
Microsoft dropping their Mobile Phone Division was mistake., Sony giving up on theirs (more or less, I mean atleast they still make them; but they're not exactly "Sony" anymore) again was too.
As they didn't fail because they were bad, but because neither was willing to continue evolving, adapting and thinking forward.
And that's perhaps even more important now; given both Apple and Google have become stagnant... they're not longer "Evolving"
I think Windows Dual-Screen is going to be kind of in the right direction., but still it's not a consolidation to focused more into one device but they've begun to segment further - which isn't what people want.
Again look back to why a Smart Phone worked.
It's because we don't want to carry a Phone, Camera, Digital Music Player, Digital Video Player, Laptop, etc.
Instead now we have a Single Device that consolidates all that into something you can fit in your pocket.
The Switch is the same... I don't need a 3DS and Wii U., instead now I just have a Switch.
Now imagine that the Switch also had inside-out tracking for the Controller Pads and folded out a conversion to be Wearable for VR... that'd be one more device it'd replace. (and a device that many do STILL want but generally can't afford)