I want to make clear that I (as the PA guy) don't consider ALSA a "mistake". It's good stuff actually. Of course, it has issues -- as every system has. But considering all the options it's not really that bad at all.
People like to construct some kind of opposition between ALSA and PA. They fail to see the big picture. ALSA is a building block PA builds on. And that's good. The ALSA and the PA devs work together. We're not in competition. If you think we are, you don't know the details.