This is a valid topic that keeps coming up, and I do agree with her responses on this, but it's not a "one" or "two" side problem here, there are quite a few things that have led to the decline in linear single player game sales...
It is a fact, that large single player games (or mostly single player), linear or not, do cost any where from around 100 million to produce, to well over 100 million depending on the exact game. So yes, they do cost a ton to make, and at $60 a pop, which is no where near what the actual profit is for the publisher/developer, that is much less, they do have to now have these games sell far more copies just to break even, not to mention make a profit which is what any normal business try to do. So these games are now becoming MUCH bigger gambles for publishers and developers alike. I mean it doesn't take a genius to realize that if you wait a few months you can't get the same game used for $15 or $20 bucks at a lot of places. So even though there might be the same amount of people crying for these games, and still buying them, more seem to be buying them from the used game market which of course does nothing for the publisher/developer.
Then you have the fact that a lot less people are buying these games (at least overall there are exceptions of course), during the normal priced time, than they were in the past. One major reason for this is value... If the single player game cost $60 and it has an 8 or 10 or 12 hour story and then your done. And you have the non linear open world sandbox game or multiplayer game that also costs the same $60, but has 50 ot 100+ hours of gameplay, or is a game as service and might last for years and years and also feature microtransactions and other ways for them to make extra money such as DLC packs etc. You now have the same price point for 2 different types of games, and the gamers nowadays understand that same $60 dollar investment can get them near limitless amounts of gameplay in one type of game, and a very small amount of gameplay and replay in another type of game (single player linear), so gamers are not able to justify paying the same price, but getting far less overall gameplay.
Then you have the fact that a larger portion of gamers nowadays love online multiplayer modes, and simply want games that offer those. You do have some linear single player games like Uncharted 4 offering a decent multiplayer component too, but must don't offer this and that hurts the sales as well.
Over all there is not "one" issue that is causing less linear single player games to be made, it's a whole host of factors that are at play here, as is usually the case with thing's like this. A few ways to possibly fix this and get more people on board would be doing things like adding decent, mulitplayer components to these games to attract a wider audience. Another thing that might work is simply charging less for them, which in the end might actually mean more sales and more profits....But of course that is risky and might blow up in a publishers face and end up costing them a ton of money. But seriously, how many of you would be whilling to buy a bad ass, linear story driven single player AAA game from a well known studio with ZERO multiplayer if the price at launch was suddenly $30 bucks instead of $60? I think that actually would cause a lot more people jump on these types of games, specially if they knew they could pick up 2 amazing, though linear games, for the same price as one non linear game.....
Of course you could also raise the price overall on games as well, which is something I believe needs to happen. Look at movies, the price of tickets has sky rocketed over the last 20 years... The price of blu-rays were much higher than dvd's etc. And people need to remember, as I have seen a lot of these comments here, that the prices of video games have not "remained the same over the last 20 years" they have actually gone down a good bit from where they were 20 years ago... Young kids here don't understand this as they were not alive, but us older gamers have no problem remembering picking up SNES and Genesis titles that were $79 and $89 bucks....Killer Instinct was $79 dollars at the game stores when it dropped for the SNES and that wasn't alone. Obviously a lot of that had to do with the format these games were on, Carts, but that same priced game now would be around $120 or $130 with inflation taking into account. It make's zero sense to have the prices going down, and staying down for all these years since the switch to disc based and digital media when the graphics hardware has gotten to the level where the detail now in games is so high it takes soooooooooooo much longer, and cost sooooooooooo much more to make than it did 10 or 15 years ago. I mean a normal AAA game nowadays cost as much as your average Hollywood action movie. So yes, something, or more accurately, many things do need to change. If we made some changes like the ones I have suggested here, and I am by no means saying that I think all of these would work, but just making some changes along these lines, that would take sooooooooooooooooooooooooo much of the pressure both financially and mentally off the publisher/developer and you would actually see more money being made, more people buying these games, more of these types of games being made again, and more importantly, more publishers/developers taking bigger risks in design again too, which will give us more variety in the AAA market. All huge wins for the industry, gamers, developers publishers alike!