Sound, like design (remember the complaining about iOS 7?) is VERY SUBJECTIVE. Seriously loads of people including myself complained about certain design elements when Apple changed everything. And guess what ? People either got used to it or it wasn’t as big of a deal for 99 percent of people to want to stop using Apple devices. I think this whole discussion will go the same way after a while. So saying the new sound is worse is not an accurate statement. Since some think it’s worse, some think it’s better and some hear no difference. Who knows how Apple will handle it going forward.
The difference with sound vs. design is that design, at least in Apple's view, is used to achieve something greater whether it's to include a larger battery, display panel, speaker, etc. It's easy to get used to it and accept it because underneath it all, there are upgrades. With sound, not one person can dictate what the best sound is for each individual. Now, if Apple released and sold the HomePod with a certain sound and never tweaked it, that's one thing. You hear the HomePod and if you like it, you buy it, if not you move on to the next speaker. But to buy the HomePod because you heard it and liked it only to have it updated where the sound changed is wrong.
Like I said in an earlier post, Apple can tweak and change the sound however they like, but they need to add some sort of equalizer so the user can tweak it to their environment because no matter how "magical" Apple markets the HomePod to be, it cannot account for every single individuals hearing and environment to come to the conclusion that this is how the HomePod should sound.