Are anime adaptations really that bad?

I've heard some of my friends telling me "anime adaptations are shit". But are they? I've seen some of them in the past and I'm not sure what to say about it.

Depends on the anime like for ex berserk sucks big time

The main problem with them is that they usually have to cut out parts of the story, so if you do wanna get the "full story" you'd usually have to read the manga anyways.

Can someone explain to me what anime adaptation means?