I'm fine with paying full price for a multiplayer only experience. I think its odd that so many people are treating this like its somehow a new thing.
It really just comes down to each particular game. I don't really care if traditionally MP only titles stay MP only, nor would I care if something like Battlefield stopped bothering with single player campaigns that were never really needed in the first place.
The difference between something like that and something like the new Battlefront is that single player or local multiplayer was such a huge part of that game for many people. I for one never went online once in either Battlefront 1 or 2. With Battlefront 2015 it feels like something is missing, but I wouldn't feel like something is missing from Battlefield at all if they removed the campaign.
The biggest problem I have seen with multiplayer only games lately, specifically shooters, is that they are not supported by content, they are supported by the grind. It doesn't feel like developers are relying on grind to promote longevity instead of creating a game players can really sink their teeth into. They feel that they are designed to get players to come back to get that next unlock rather than trying to get them to actually play the game.
Its all about giving player 'choice' and giving them all these 'options', but at the end of the day the choice amounts to nothing as the vast majority of the unlocks are worthless in a practical sense or redundant. A few of the better combinations always float to the top leading to far less 'variety' than the huge number of weapons, attachments, perks, characters/classes, etc would lead you to believe.
Once the grind is over there simply isn't much to do in so many recent multiplayer only games because the grind is the game, without a single player or other lasting content players burn out on the multiplayer and by the time they might feel like revisiting it the game is dead and/or the servers have shut down.
It gets worse when you consider many of these games heavily push pre-orders and microtransactions. Most of which end up being ways to avoid the grind(that the game is designed around), which only makes the player burn out even faster. Great for the publisher who want to get a lot of money and avoid paying for servers in the short term, terrible for the consumer.
So long story short I would say a the exclusion of a single player campaign is justifiable, but full price multiplayer that is only held up by a skinner box is not.