Well, the Steam Deck's release coincided with the popularity of reconstruction techniques. The Deck didn't "force" devs to consider optimization so much as it just gave them a low-end reconstruction target to play with. Without FSR and XESS, there's no doubt that the Deck would be a solidly last-gen console.
Strictly speaking, a lot of games really shouldn't be playable on the Steam Deck. Baldur's Gate III and Cyberpunk 2077 are both CPU-bound before reaching 60fps and can barely keep their head above 30fps running at 360p internal resolution. The Deck's saving grace is that it can tap into the same dynamic resolution mode that last-gen consoles depend on for consistent framerates.
