In theory, enthusiasts could pay to keep the lights on even after the developer went out of business.
https://partner.steamgames.com/doc/sdk/api/example provides a good example, too. Steam has all sorts of extra functionality to justify their 30% cut on sales, they're not just taking it while doing nothing.
It's astounding the frequency I get an email from some cloud provider, or mobile app store that says something to the effect of:
"(Version X) of Dependency Y that we convinced you to use 5+ years ago is getting deprecated on August 1st, if you don't upgrade to Version X+5 you're service will go offline"
And we're stuck looking at the minimal amount of players running of that platform, and the hard choice of do we move precious human resources off of some in-progress game, that's already running late to learn a system that they never worked on, because the original people are long gone?
So, that's often why our network services, and mobile versions of our games are being taken offline while the single binary we shipped to one of the serious console vendors 10-20 years ago is still running, and now running on consoles 2 generations newer.
So, yeah, it'd be great if we could ship a package for Amazon to host perpetually, but first you could just get Amazon to care enough to ship a stable platform to build upon that wouldn't get depreciated.
But then, having also lived it, upgrading to newer versions of PHP and it's required modules is also not trivial.
And it's often not just your language, the cloud vendors have a lot of incentives to get you to use their hosted Postgres, or AuroraDB, or GameLift. Or even something as simple as we built all of our deployment scripts/images for our PHP system on Amazon Linux X, and now for reason Y, only Amazon Linux X+2 is supported.
I also doubt that such a could service would be immune to corperate restructuring by the like of Amazon. We need gaming companies to be more comfortable providing server binaries if we want anything that lasts.
I run my own private server for a live service game that shut down in just 1 year. We got lucky because they seemingly bundled the server code into the client. But the game was never meant to allow for that...