Like most things in the js ecosystem, it likely never will. It'll be a best effort, chasing the standard with usability and accessibility gaps littering even the best libraries. But hey, there's rounded corners that glow, so totally worth it.
Those libraries often cover edge cases the spec doesn't. For example with this what if for some reason I need the top level to share a some permamently available UI element?
But more seriously, you do this in multi-page apps by just having that UI element in every page. Just about any (server-side) templating system lets you do that easily.
Sure, but is <dialog> going to work seamlessly with that if it isn't aware of positioning outside of the top layer?
It could be that it is, but this is just an example of the kind of relatively common case that these maligned libraries cover that the spec often doesn't acknowledge.
