Sorry for the title mistake.
Was talking to some Sr friends at 2K not too long ago, and while there was a bit of a select resurgence a couple years back - there's seems to be a big overall question about the future of big single player games as a whole in the industry these days. The "resurgence" didn't seem to last into this generation as games move more toward services, and for all the reasons you mention
I feel it was actually a really weird decision for publishers to back out of having multiplayer in their games heading into this generation.
Like, I get that the logic was "Well, having this bad deathmatch mode or this bad horde mode isn't getting us any sales, so let's just dump all we have into trying to make the singleplayer better.", but it felt like it was ignoring the actual trend that was going on, which was a polarization around the biggest and best games, some of which happened to only have singleplayer. If you just project this same scenario a few years down the road to the point where everyone is delivering a pretty high quality singleplayer experience, suddenly multiplayer becomes a major differentiating factor again.
Then, late last generation, and especially with this generation, we had a variety of really ambitious online games that heavily incentivized you to play with friends. Even beyond the service model that sees these titles constantly updated, I feel publishers missed a really important impact that these would have: If you're frequently playing games with your friends online, you're more and more likely to keep doing that. Suddenly, someone that might have played two or three singleplayer games a month now finds it very hard to find gaming time in which to play them, because they want to be playing games with their friends instead. You basically have to offer an incredibly good and unique looking game to get them to part with $60 and sit there for 20-80+ hours ignoring their friends during their gaming time to play your singleplayer title instead.
I think we saw Dying Light take advantage of this scenario very well. It offers a cinematic, singleplayer-style, Ubisoft-esque open world game, but you can basically play the entire game in four player co-op. It also made sure to make the core gameplay feel very good so that it worked well in co-op, it didn't eschew any of the story, set pieces, or production values you'd expect out of a singleplayer campaign game, and gave you a wide variety of options in terms of what to do when playing. The game ended up with over 8 million players according to Techland, and to have an incredibly good reception from both multiplayer and singleplayer gamers.
I feel there are a ton of games missing out on the opportunity of making a similar product, where it's a lot like and maintains the quality of the singleplayer games people enjoy, but can be played co-operatively to attract multiplayer gamers. I'm actually very bullish on Ghost Recon, assuming it delivers on quality, since it delivers the Ubisoft and/or GTA-esque game experience, but with full campaign co-op. Watch Dogs 2 and Assassin's Creed Unity offer co-op, but only in special content, which is a much less compelling proposition.
That said, the amount of job postings I see at major studios that were making singleplayer only games that now list requests for multiplayer experience, suggests to me that publishers are realizing the issue facing them.
For my own personal gaming tastes, I can get behind this. In the rush to attract the "core" I think a lot of games are trying to have systems in order to cover being an action game with RPG elements, stealth mechanics and crafting systems. Personally, I'd like to see more games like DOOM. Pick what you are, and be really good at that one thing.
On the note of Doom, I think the other thing Bethesda really nailed is the pricing promotion structure. The game went on sale for $30 very early in its lifecycle (I believe month 2?) and, at least on Steam, saw an astronomical uptick in sales. I think it made way more sense to do that early when people were still excited than when people weren't excited anymore and only selling to them for $15 instead.
I think they recognized that they had a high quality product that targeted its audience really well, but that it was also somewhat of a hard pitch at $60, and aggressively chased their market at a price point they would be more comfortable with to great success.
Given that Titanfall 2 seems to have had some good recovery this month, I suspect EA's similarly aggressive pricing strategy ended up helping that title out a lot as well.
There's probably a lesson to be learned here, and some questions around business model to be raised. Though, one difference between Doom and Titanfall 2 is that Titanfall 2 has a notable multiplayer mode, so the service model around selling extra content to make more money on the back end is a lot easier than for Doom, which certainly has made a valiant effort to be a service game, but is a harder pitch due to the multiplayer mode being relatively unattractive. I did notice they added the ability to make co-op campaigns in the map editor though, so I'm curious if they're also considering co-operative content in the future to play more to their strengths in future multiplayer components.