But everyone knew or was at least informed that it was a multiplayer only game, presumably online play.

It should absolutely influence the decision to buy the game, but it's not like this is the first time a major release has taken this approach to development.

Unreal Tournament 3 from 2007 was for all intents and purposes a multiplayer only game with a fairly basic campaign that consisted of an over map with narration explaining why the player was doing X type of game in X arena. No one bought it for campaign mode. Since players were almost exclusively playing it for the online multiplayer, minimal resources seemed to go into the campaign mode and maybe this is why developers of Titanfall chose not to divert any resources away from the online mode.

You have to look at it in terms of overall development and marketing budgets when it comes to pricing. All the resources went into online, there were no budget restrictions with regards to the in-game content (models, textures, environments, characters, etc.) and it has been marketed as a major release title as it should be.

I suppose the biggest disappointment should be from players who wanted the XB1's Gears of War or Halo with regards to an epic, fully developed, playable story.

The lack of players is a disappointment too, i'm bored. ( the loading too much long dont help )

but the biggest disappointment is the lack of splitscreen in multiplayers, it is very sad for such a game. COD has one and more players at the same time.

I think the little kids that can't afford anything on their own and asked their mom and dad for the game and didn't bother checking the live requirement are in a stickier situation.

don't most people love multiplayer with these shooters though,i thought thats why they play them and why they are popular

Gamestop employees let them know all the time. 

I got it for free with my Xbox One. I'm okay with that. What bothers me is the graphics aren't impressive at all. Game is fun as heck, though.

If you play a SP only game, do you ever complain about how there is no MP mode and how that's cheapening the value of the game? No, you don't. In fact, most people get annoyed if a dev puts tacked on MP on to their SP game, telling them to focus on the SP mode more and make it even better than tacking in MP. So if that's the case for SP games, why can't a dev put all their efforts and make a highly enjoyable, full blown MP game without putting on a horrible tacked on 4-5 hour SP mode that has no replay value like in most shooters?

If a SP dev can make a solid content filled game that has no MP mode without making you feel that the value of the game has been cheapened, then a MP dev should also be able to do the same with a good MP game with no SP mode. If it's the contrary, then just don't buy the MP game. I will personally buy a game, whether it's SP only, MP only or both depending on how good the game is and if it's fun enough to deserve my money. I don't have a preconceived notion of a game NEEDING to have either a SP or MP mode for it to be good value for money.

I have 2.0 in COD and have played for multible Prestiges on every game but I did enjoy the SP for all the games.

Really because I can remember every single game before this doing a SP.....

There's nothing wrong with MP games as long as there worth your money. Some of the very first video games were MP only dating back to the early 1950s. Gaming has always been a sea of SP and MP games. This isn't anything new its just MP games are starting to find there own feet again while SP games have evolved into the movie business.