Halo 5 is a game as a service with the free expansions but microtransactions. That doesn't mean that Halo can't be also a great singleplayer game (well, in a normal case, not if they fuck it up lol)
Games like Horizon Zero Dawn or Zelda aren't games as a service but they could be one and have still pretty much the same campaign to play alone.
So, we should wait and see how far they go with it. If they will just kill singleplayer experiences in most games or if they will just implement stuff to let some people stay engaged with games to let them pay for weird stuff nobody needs normally..
GTA is an example of how it worked, it was and still is also a singleplayer game but now it generates probably 90% of money "as a service" and Red Dead Redemption 2 will be the same (well, RDR wasn't a singleplayer only game but also not a game as a sevice and I'm sure it will be one now)
There are also games which I can't imagine as games as a service (like Heavy Rain) but if they won't have any game which doesn't work as such a game at all is something we have to see.










