I've been on quite a few cruises and have cruised Royal, Norwegian, Princess, Costa, Celebrity and Viking.
I can honestly say I've never been on a "bad" cruise with any of the lines. Sure I've had some negative experiences, but nothing that outweighed the great time in other aspects.
Too many times on CC those that post tend to dwell on the negatives rather than positives of a particular cruise or cruise line.
I've made the choice to keep my focus on enjoying life and enjoying cruising. If I ever go on a cruise that I can't find positives to outweigh the negatives, I should probably stop cruising.