I guess it's all relative. Lucina is unique compared to Marth and Ike at least.
You can say the same to Chrom as well, because Lucina is the exact same as him in Awakening.
Awakening is also the best rated fire emblem, coming in at a 92 on metacritic with a user score of 9.3. Calling the game **** is pretty much just wrong.
Meta critic means nothing. Or do you think GTAIV is top 5 material?
Awakening:
-Terrible map design. They're usually empty and wide, with enemy placements being at complete random spots.
-Most of the difficulty comes from same turn reinforcements, often without prior warning. (And when there are, it's never ever a good indication.)
-Despite that, even the littlest grind can make anyone overpowered. Second seals and pair up ultimately break the core formula.
-Repetitive. Repetitive. Repetitive. Awakening sticks with same ideas and never changes up.
It's given a pass of the game is designed around experimentation rather than tactical thinking. By virtue of experimentation the map design is excused (when it shouldn't) because of the endless possibilities you can make out of your team that is made possible out of pair ups and second seals. (This is seriously what EVERYONE praises it for.) The game is accessible unlike other FE games which to first timers think makes it amazing because the core mechanics is still fun, and with that they're not familiar of the good map design the series is pretty much known for. The game is mechanically simple, but not in a good way because all the complexity was clearly stripped down.
I mean, it all comes down to preference. I wouldn't call it a bad game overall per se, but a bad Fire Emblem game? Easily.