Final verdict: no we weren't too harsh.
Pros:
- Space!
- PimpCommander
- Balance
- Octopussy's personality changing every time she came back
- Tsurugi (even if he couldn't keep his damned shirt on). And his verbal tick/catch phrase wasn't actually all that bad
- The Dark Naaga arc
- The Orion arc (hell, let's just say everything in the 20s other than the clip show)
- Episode 7 v4.1
- That Toei somehow let Kyuutama Dancing v1 out in the first place, despite the obvious problem of having repeated hip thrusts in a dance
Cons:
- Lucky!
- That Kyuuranger didn't actually spend more than a handful of episodes on worlds that were actually alien in some fashion
- Too many rangers meant that most of the characters were underdeveloped
- I'm not going to say that suit characters are wholly inappropriate (see: Balance), but it really doesn't help matters that they can't emote like the humans can. So this ended up being a series with the normal number of face actors, and then a bunch of gimped actors
- Any time Stinger sung
- That the plot thread of Don Armage hiding the existence of Tsurugi and that Earth used to be more advanced was almost immediately dropped
- Garou after episode 1
- The villains in general. They were poorly defined and, outside of the one that corrupted Naaga, didn't do much that ended up memorable
- But especially Don Armage himself. This was yet another year where the Big Bad did plenty of evil, but for no discernible reason. "I want to rule the world" can work, but the Big Bad better be damn charismatic and appear frequently to pull it off
- That Octopussy came back two times too many
- The mecha. 9 of the 12 Kyuurangers were technically just limbs for Red and Purple. And even "limbs" is being generous since they mostly just filled ball-shaped holes in the body.
Ultimately the series isn't as bad as Ninninger, which sets the low bar for a bad modern Sentai, but it's certainly down there. What saves the series is that it had some nice arcs in the middle; some good highs. But it's equally damned by all of the arcs that sputtered (Prince Lucky), and the general problems listed above. Whereas Jyuohger was mediocre all the way through, Kyuuranger is a mediocre series on average.