While I think people have been especially harsh on this series, there are a few problems (as I see them):
Pacing: I'd have to verify, but I was thinking the three previous series ran closer to 45 minutes per episode, while each Iron Fist episode ran around 55 minutes. Every episode had at least one point where I was checking the clock to see how much time was left. Tightening up the self-analyzing and philosophical debate sections would have helped everything flow better.
Character Development: When your title character seemingly grows the least over the season, there's a problem. I hate to blame Jones directly, as it could have been the directors and/or showrunners making some odd choices on the portrayals. I really feel by the end, Ward Meachum and Madame Gao were the most compelling of the cast. I was on board with Harold until the last two episodes, when he turned from background manipulator into one-dimensional, monologuing Bond villain. Likewise, Joy and Davos turning evil at the end... really? Davos I could buy since maybe if Danny dies, he'd be next in line for the Fist, but Joy seems like a major shift from how she was up to this point.
Fight Scenes: I hate the jump-cut, frenetic editing that seems to be the vogue these days. Since martial arts are the focus of the series, how about letting us actually see the fights instead of cutting the scene every 1/10th of a second?
I have a few more specific issues, but that jumps into major spoiler territory. Admittedly, I'll probably watch Season 2 when it comes out, but I'm hoping the creators saw some of the criticisms and make some positive changes.
Honestly, the entirety of Iron Fist Season 1 felt like the lackluster second halves of Daredevil Season 2 (Hand/Elektra) and Luke Cage Season 1 (Diamondback).
