Ehhhh OSS is really not great, even v4. Re-using Unix file I/O functions for audio sounds clever, but falls apart pretty quickly in the real world. Even in the best case where you manage to shove every audio feature into open, read, write, and ioctl, it's never going to feel good to use (type safety...).
I don't mourn the loss of OSS.
OSS relies on mixing in the kernel, which is bad for reasons explained here: https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/FAQ...
Also with OSS you still can't seamlessly switch between devices, bluetooth or arbitrary signal routing between apps. So, no... good riddance.
This is a clear case of when ideology won over an objectively better product to the detriment of all users for more than a decade.