It has mechanics: It has a parry system, ninpos beating lower ninpos, guarding, and a break mechanic which allows you to escape combos and ninpos at the cost of 10% hp. The game isn't balanced character wise but there are good and bad MUs, but this mainly applies online.
It's kinda a hack and slash so there's action as far as attacks and fighting goes, the story is pretty good too, it's funny and lighter hearted near the beginning but gets more serious towards the end. You'll have to play online and complete the shinobi heart missions to get the most out of though since the story ends like any other game, the ending makes me cry every time..
Like, aside from Senran being niche, I wouldn't be surprised if people were turned off by its fanservice especially the later games. It's really over the top.
My friend who made me try the game also told me his female friends tend to like it while the guys shun it lol.