That still is the case, it's just that nobody runs hardware DSPs so nobody needs to deal with anything but a single userspace sound server. Video just has order

That still is the case, it's just that nobody runs hardware DSPs so nobody needs to deal with anything but a single userspace sound server. Video just has order-of-magnitude higher processing requirements, so dumping raw buffers into userspace and letting a "video server" do the work isn't usable for use cases that care about latency, throughput or resource usage (e.g. game streaming). So you end up with a bunch of kernel interfaces for hardware-accelerated video transforms (many driver-specific), a few competing userspace APIs (gstreamer, vulkan extensions, vaapi, vdpau, etc), zero-copy kernel buffer APIs, the list goes on. You end up with something like Pipewire just to abstract over the complexity.