In universe, do you think having black ops teams is a good thing or not? And in what situations are they necessary or not necessary?

Those teams are more inclined to use lethal force, so they're necessary in situations where lethal force may be necessary.

Or politically dangerous. Regular superhero teams are the police and the military, Secret Avengers and X-Force are Special Forces or CIA Paramilitary. If spec ops are necessary in the real world, they're necessary in worlds where people can summon demons, read minds, and throw buses.