The fact that this game is a rip-off doesn't make it bad. Or even mediocre.
While this game has absolutely zero originality and has the word "rip-off" glaring all over it, it stands out from the crowd of identical Battlefield knock-offs. What makes it stand out? Two things: it's Star Wars... and it's good.
Just like in Battlefield the storyline has been thrown out of the window. However, it is easily explained: why would there be a storyline in a game that doesn't care about its singleplayer. Singleplayer amounts to about 30% of the game and it is definitely just an appetizer for the awesome multiplayer experience.
What makes this game different from Battlefield? The Star Wars license. A lot of work has gone into adapting and it really shows. First of all, the environments are simply fantastic, especially the ones from the original trilogy. Second of all, an interesting gameplay element has been added. During the fights on some planet, a 3rd faction interferes and they are usually hostile to both of the armies. Those factions can have a large impact on the result of the battles which makes them unpredictable. Lastly, there are battles during which one side is assisted by a Jedi or a Sith and they never die unless you glitch them or throw them from a cliff.
I could speak about the classes but they are identical to Battlefield. Same thing goes for weapons (tanks replaced with AT-AT walkers, jets with X-Wings and Tie-Fighters).
You can call Battlefront a rip-off, but I would call it "a worthy adaptation of a very successful idea".