How does this episode manage to be both good and dumb at the same time?
I have adopted a certain mindset: Nothing wrong with clipshows/flashback episodes, as long as you do something with it other than make it about the clips/flashbacks. Examples include advancing the story in a minor yet important way, answering some plot holes that have left audiences confused, or introducing a new plot point that will become relevant later. This episode chose to do the latter.
I like the idea of Koh being able to hear the voice of Ryu Souls. I like the idea that Ryu Souls eventually die out and need to mined in order to be replaced. The Wish Soul was very intriguing. And while I still don't understand the difference between transformation Ryu Souls and regular Ryu Souls, I like the idea of a Kishiryu converting its soul into a Ryu Soul.
However, why in the world would the Ryusoulgers need to trade amongst each other? I know some don't fully trust each other, but if they have a united enemy, wouldn't it better to pool their Ryu Souls together instead of keeping certain Souls to yourself? Obviously, I'm not talking about Souls that can only be used by one specific user, like the Burning Soul. And if the Ryusoulgers are going to be sticklers about ownership, then how is trading easier than just going out and mining for new souls? Seems like only the rare types are worth trading, and even then it might not be worth it if you can't access its power.
And finally, there is the ending...
I mean, can I get mad at it? Should I even bother? We all know casting the Wish Soul into space was a dumb idea. It's going to make a reappearance. If anything you just made it a bigger target, and keeping it close would have been better. But this is hardly the first time Super Sentai has done dumb things like that, and sometimes it actually works out. It's become a reoccurring trope at this point, so is complaining about it really going to accomplish anything?