If a browser doesn’t support any of the APIs, the user always sees the content. It works, but it’s just not enhanced using progressive disclosure. Importantly, we’ve made sure the experience isn’t broken for anyone. That’s inclusion.
I'm not sure how we've got to the point where we're okay with not supporting people on older devices.
"They can always upgrade, Charlie". No they can't. YOU can upgrade your laptop. Someone who is poorer may not be able to. And when they can't upgrade the device they're stuck with an under powered CPU that may not render the latest fanciness. And they often can't upgrade to the latest versions of browsers.
But please, carry on building essential services that can't be used by some people.