The only way for it to last would be for browsers to compile into some kind of compatibility layer for newer GPU features on older hardware, but that’s probably going to be extremely tough to do in some cases without killing performance on the older platforms, particularly if those features relate to things like synchronization.
Newer mobile GPUs worth a damn pretty much have the same feature set as desktop.
Except texture formats in case of Mali and Exynos w/ RDNA. But QCOM (since quite a while) and Apple (E17+) have a unified set there including BC7 support.
So perhaps split things into profiles, with a more modern profile where the only thing varying is texture format support.
