Huh? Who said that? Even the developers always claimed it's a FPS.
Anyways, it got depth, an incredibly well realized world and story, interesting gameplay, and still tons of possibilities to improve your character via tonics and plasmids, and is definitely worth picking up, even if the tools used to tell the story is completely unlike Bioware games.
It's simlilarly strucured to System Shock 2, although the core experience is improved, and some things are worse (like the lack of an inventory).