I would agree and disagree.
On the one hand, it's hard to deny that games like Banjo-Tooie have for all intents and purposes disappeared. These days it's very rare to find a game which intertwines its world and various areas to that sort of degree in the effort of making what appears to be a living, breathing world.
But on the other hand, most games of the 80's and 90's were criminally short. Yahtzee should know better than most of us, given his track record of adventure games which he replays for the internet's amusement. Most of those games can clock in under 2 hours, and the only qualifier for it is "if you know what you're doing". Because that's how older games tended to seem like they had more content; They had such a prohibitively high difficulty curve that you could spend days, weeks, even months and never actually complete them. But once you know what to do, you can breeze through most of them in a single session.
The very late 90's/early 00's are a better comparison, because that's when you have the Deus Exes, the Baldur's Gates, the Banjo-Kazooies, but even still it's not as if there were no games made during that time which clocked in with really low average play-times. I don't feel it's a particularly new thing for games to be released with a "smaller" amount of gameplay, and I'm not sure that having less content is inherently a bad thing.
Arguably when the title is still being sold at $60+, it is, and admittedly AAA publishers are too afraid of collapsing to even dare attempting other price models that aren't somehow even more exploitative, but I often find that games which try cramming in tons of extra content to justify their price end up feeling too poorly paced or stuffed with useless filler. Arkham City's sandbox may have been relatively small, but I liked it for that because it felt like I was always making progress in one way or another, whereas in something like Grand Theft Auto or Assassin's Creed or Saints Row: The Third or even Sleeping Dogs, most of the side stuff just feels like they tossed it in because that's what sandbox games are supposed to do.