Terrible because James Gunn wrote it by himself
James Gunn fought Nicole Perlman (the first female scriptwriter for a Marvel film) for sole writing credit on the Guardians of the Galaxy script.
Marvel let Gunn write Guardians of the Galaxy Vol. 2 by himself (maybe to start positioning Gunn as their new Joss Whedon) and the results were, IMO, mostly saccharine, self-indulgent and dumb.