If you're talking about FEH (Fire Emblem Heroes), yes, it is a gacha game. Despite what its detractors may say, I would suggest giving the game a shot if you simply love Fire Emblem, and the idea of building up your favorite units.
As a forewarning, it's incredibly different, and exceedingly more complicated compared to it first came out. Here's an example:
On launch, "Distant Counter"; a skill that let your melee units counter ranged attacks, was one of the most coveted abilities. It was so powerful that if a unit had it built into their weapon, it would be their weapons only effect.
Now? Distant Counter is a dime a dozen ability that every unit can access. What's more, weapon and passive skills went from being one, two sentences at most, to being straight up paragraphs, rivaling that of Yu-Gi-Oh! cards. If that doesn't sound up your alley... then the game is a hard sell. I will say though, despite how much more complicated skills are now, and how they continue to do so, FEH is still a gacha. And it's always easier to get started in a gacha the later you start, because of how many resources you have at your disposal.
I've been playing the game for 9 years every day, and I still love it, warts and all. However, I also don't take it "seriously" by min-maxing my units to score uber well in the competitive modes. That's a lot of time, planning, and money that I don't want to put into a gacha game.
All this to say, if the game interests you, try it. If you like it, great! If you don't, then oh well, at least you tried.
And in the event you were talking about Fire Emblem Shadows... I don't play that so can't help you there. All I can say about that game is that the designs are really cool.