It's more than 20 years later and still I don't understand these complaints. ALSA was designed to have a broader API than OSS, and it has supported OSS emulation for quite some time. What else could have been done when OSS went non-free?

PulseAudio and PipeWire embody the correct approach. The problem with OSS is, if you're using anything resembling modern audio formats, it risks introducing floating-point code into the kernel, which is a hard "no" in mainline Linux. So if you need software mixing, it should be done in a user-space daemon that has exclusive access to the sound card.

OSS was the last time I had Linux audio in a state that I would call "basically working".