The article is a bit vague, but looks like there are two direct problems:
Firstly that some functions will simply stop working over the. Article doesn't say what, and as I don't have a Sonos system, I couldn't guess.
Secondly, newer devices won't update with an obsolete device on the network. Looks like Sonos is fixing this, but it's such a weird and unexpected problem to crop up in th first place.
Traditionally, good audio equipment should last decades easily. If I had the space, I'd be running audio gear from the 70s. After a couple of decades, capacitors might start to bulge, but these are replaceable with a soldering iron. The gear that currently have, which is modest, should last me the rest of my life. I won't have to worry about replacements or upgrades, which I personally find relaxing. Versus, say, buying a computer which I think about how many years it will last in its primary role before having to fold into some secondary role.
Sonos to me isn't so much dedicated audio gear, it's convenience lifestyle gear that happens to play music. Which is fine, but from some of the negative reactions to the products going end of life, it looks like some purchasers don't realise what they're trading off against.
Edit: I should add that I'm not against what Sonos is doing at all, I think five years is totally reasonable for this kind of product.