In my opinion it's not a marketing failure. The combination of paying full price for games that require the service combined with Google's reputation for killing services left it pretty stillborn.

I think Google may have realised this which is why they're carefully managing the shutdown. It was too late for Stadia, but they don't want consumers feeling the next service is risky too by showing an intent to make it right when the shutdown happens

“It’s not a marketing failure” and blaming it on perceived vulnerability to cancelation of the service are mutually contradictory claims.

On some level maybe, but at this point no amount of marketing is going to change Google's reputation.

I disagree. Everyone that I know who has even the slightest interest in video games has heard about Stadia. They can't market their way out of the public perception around Google's long term commitments, nor can they change the laws of physics to eliminate input lag, nor can their marketing change the perception that paying full sticker price for games only accessible through their walled garden streaming service was a terrible deal.

They likely would have gained more popularity had they promised to refund all purchases in case the project shut down in less than a decade - in a legally binding way. This would have given customers a lot of confidence to invest time and money into their platform.

Additionally, they could have pulled in a portion of the existing PC gaming market if they allowed users to bring their own games. Having a service that would allow you to play your existing library while you're traveling or over at a friend's house would be enticing to many.

I wouldn't call this a marketing failure, however.

It's not a perceived vulnerability, it was a real, fundamentally unavoidable vulnerability, which is why we're here talking about the aftermath. This is why I disagree that marketing could have solved it.