It is the lack of content in relation to the full price and the season pass strategy, again for full price.
For decades people managed to play shooters because they were inherently fun before CoD4 introduced a progression system.
If there's a constant flow of new maps and stuff, it can be kept fresh. However, I do think tastes have changed. The conditioning to progress in modern gaming (mobile as well as console) means a lack of progress tastes a little plainer.
The game's problem is the lack of content
together with the lack of a rewarding progression, both of which are limiting replayability. There are only 4 (
four) maps that support Walker Assault - which is the only mode that anyone wants to play because of the higher player count and vehicle availability, save for the curiosity of trying the other modes once or twice.
Battlefield 4's initial
vanilla release in comparison brought 10 maps supporting the equivalent "flagship" mode (64 players + air/water/ground vehicles). Moreover, the weapon variety was immensely larger than Battlefront's and each weapon was customizable through ranks and points. On top of that, the game has character classes (just like previous Battlefront titles) which have to be progressed independently. Plus, there was a single-player campaign.
Battlefront has none of it.
Between scarce map variety, lack of weapon variety, lack of classes, lack of weapon customizations, lack of vehicle variety and lack of single-player campaign, Battlefront's initial release has probably close to 1/4th of the cheer content that Battlefield 4 brought on day one.
In the end, EA decided to release a game that manages to please almost no one after the initial honeymoon period of 10-15 hours.
A pure online game on the mid/long-run is only as good as its player base. If there are no players in their servers, no one is going to buy the DLCs - which is where EA seems to think the golden eggs are.