If you're not, it might still be for you, but would probably suit an open minded approach.
It's a fighting game starring lead and supporting Gundam from basically every Gundam series ever, which is a lot of Gundam, and if you have no frame of reference, not much of it will make sense and you'll probably just pick the coolest looking Gundam.
If you are fluent in Japanese, or have memorized your favorite Gundam pilot's catchphrases, you'll probably enjoy this more, as the voiceacting is all Japanese (good) but not subbed at all (less good). The graphics are crisp though, and any text is properly translated so you (mostly) know what you're trying to do.
The game doesn't do much in the way of explaining anything anywhere, so you'll probably spend a little while trial-and-erroring your way through, from figuring out how to attack to figuring out what each Gundam does differently, exactly.
The game is clearly designed for PVP, and has no story modes or anything like that, but the single-player survival, “route” battles and custom battle mode will probably give you enough mecha to plough through and satisfy your Gundam itch without having to go online and get your Ahab Reactor shoved in by an enemy pilot who's done nothing but play Gundam VS since it launched.
The actual combat is alright, although for a game based on an anime where people dart about in giant mecha, it's a little stiff and hard to feel properly awesome in. (Compare and contrast: Devil May Cry, Metal Gear Rising, or even Titanfall)
TL;DR: You'll either really love it because you're a massive sucker for Gundam, or you'll find it a difficult child to love.