Shadow Moon is something that I feel needed the build up towards.
It's why I don't mind the episodic nature of the show, though I will argue bitterly about the plots Gorgom had as most of them made sense. Not all, but most.
The wait for Shadow Moon builds him up, I feel, so making him show up is a big deal. Then after that the show kicks into high, because once Shadow Moon shows up, its the herald of the end. They can't have something like him around for long before getting into end game stuff, so of course they had to stall before bringing him into the series.
The filler in between was smartly salvaged, despite apparently being temp scripts, and had a lot of great action and great monsters. For filler, it can be worse.
Also Glam, in your list you neglect to have the death of the human doctor played by Hayata's actor from Ultraman, the very next episode after Biru's first appearance. This baffels me because it matters far more to the plot than the silly "Biru tries to one up Roadsector" story you DO have listed, which I do like but is more filler than the former, which involved the death of a semi major character and the showing of Biru's talents even further.