I mean, I wouldn't say it's one of the worst seasons of any TV show ever... actually, yes, yes I would. It has a lot to do with the original showrunner leaving to do Flash, which starts alongside S3 (and has a few crossovers). The new showrunner basically pandered to the absolute worst portion of the fanbase and turned the show on its head.
But S5, which just wrapped this past week, was a pretty good return to form. So, it does get better.