I can't really agree with that assesment of Valves past hardware.
Steam Machines were DOA, and anyone that actually bought one from one of the manufacturers likely got one that came with windows installed, because valve delayed the controller and software for so long the manufacturers pivoted to putting windows on them to be able to start selling the inventory. That meant very few that actually run SteamOS made it into the wild, most of them getting sold as just console-sized windows PCs.
And if you still have one, it's just a PC. You can slap Bazzite or Windows on it and it'll work just fine even today.
Both steam controller and link continue to get software support, and also function to this day. Valve stopped manufacturing and selling them, but support has not stopped.
No matter how you look at it, buying valve hardware has meant that even as it ages, they make sure it doesn't turn into a brick, or even have its usefulness compromised.
Same goes for the Deck, Valve couldn't brick the thing if they tried. When you buy one, you will still have what came in the box ten years from now.