The problem is there are a lot of characters in these movies. X-men fans are used to have detailed backstories because it is usually the case in comics.
But in the short time of the movie, it’s not possible with so many characters. So they use “archetypes”: the “femme fatale” (Emma Frost), the power-hungry villain (Shaw), the henchmen (the rest)…
It’s only frustrating if you see the movie thinking of the comics.