Marvel's Iron Fist was something of a streak breaker Netflix's Marvel shows. On its own, Iron Fist wasn't totally irredeemable, but the show was still subpar at best, with the bad certainly outweighing the good.
What made it such a crushing disappointment is that Marvel was on a roll with Jessica Jones, Luke Cage, and both seasons of Daredevil, and Iron Fist didn't even come close to living up to that standard.
Among the show's many faults was the titular protagonist himself, Iron Fist (aka Danny Rand). He was immature and petulant to the point where it was annoying, he wasn't nearly as engaging as some the other characters on his own show, and Finn Jones was a questionable casting decision, to say the least (not even factoring in the fan backlash the series received for going with a white actor, as opposed to tacking the character from a different perspective).
However, with the release of the crossover mini-series, The Defenders, it seems as though there is hope for Danny yet. He still has a way to go, but this show has taken one giant step forward in salvaging the character of Iron Fist from the ruins of his solo series and turning him into a character fans can get behind.