I think the point is that if we allow the "but you can airplay" argument to apply so readily- which, by the way is jettisoning the "smart" half of a smart speaker- then it's just an airplay speaker. Airplay is available in all kinds of setups. My receiver has airplay. So let that be "good enough" and I definitely do NOT need HomePod as I can just airplay to what is very likely to be much better speakers via airplay.
I perceive the point of this thing is the "smart" piece. I don't think it can "win" on quality of sound for much beyond maybe a launch window because all of the competing players can always put a better speaker (hardware) into their cut of this kind of thing, just like you or I can quickly upgrade the speakers in our car by swapping out some hardware. The magic in all Apple products is the
software. Strip iOS or macOS and you have mostly commodity hardware left over. Siri is the bulk of the brains in this smart speaker. Strip Siri because we're applying the airplay "solution" and what's left?
If we try to make this a "do everything" device via airplay, there are LOTS of alternatives for airplay, including many probably already in place in our homes... for far less than $349. For example, along with that receiver, I can airplay to my

TV. I can buy 2

TVs for the price of 1 HomePod... and get all of the other

TV benefits- including Siri voice controls with the very same Siri "can't see my own ripped content" limitations.
None of that is meant to put the product down, just point out how trying to make it much more appealing because- conceptually- we can airplay everything- is not the same as making up to everything work inside it. I can opt for Pandora on the

TV if I like. Can I do that with HomePod? Apparently yes, via airplay, but is that the same? If the "smarts" are actually outsourced to other devices (the airplay source), does it become only a speaker at that point?