My dad had a stereo system to die for, but he also had Sonos, because he wanted to listen to music everywhere in the house. For a while Sonos was the only game in town.
They are no longer. The iPhone makes a great controller. Spotify and Tidal mean we don't need a local file store. Speakers from Bluesound, Amazon, Google and Apple compete at various price points at the low end. If you do want to spend on a local controller, then Roon, a spin-off of ultra-audiophile Meridian, has a better experience than Sonos, and is supported by brands like Meridian, Naim, Nad, Trinnov and $100 hifiberries.
I have Mission speakers in the bedroom. Meridian speakers and a hifiberry in the lounge. A 7.1 system with another hifiberry in the TV room. Bluesounds in the kitchen and dining room. And the bluesounds have battery packs, so I can carry them into the garden if it will ever stop raining. With Roon, they all play the same music in perfect sync. A new "remote" cost me $49 for a 7" Amazon tablet, but I can also use the phone in my pocket, or the iPad upstairs.
So Sonos is competing with Echo Studios, Bluesounds, Apple and Google, at the low end, and it's being beaten by a pure software company who is integrating with audiophile kit at the high end. That software company charges a subscription. It's not relying on hardware sales, just as those sales are getting killed by cheap competitors.
Meanwhile they've got legacy kit. IIRC the original stuff set up its own wifi network that it controlled in a proprietary fashion. Nowadays, competing devices just work on whatever you wifi you got, and I assume Sonos' newer devices do too. That can't be fun to sort out, hence the "two networks" solution. To be competitive, they have to cut the old stuff loose.