You keep saying that, yet your arguments are weak. All you're saying is that Kabuto threw out a bunch of implications that we should assume meant this and that. That is not good writing. That is incompetence.
I personally disagree. If the action makes sense considering other information available, it doesn't need to be explicitly told. Obviously, you disagree and would have preferred a scene showing those events directly, but, just because you didn't like the execution, it doesn't mean those events didn't make sense.
Why do people always say Daisuke's lack of relevance is defensible? What is the point of introducing a Rider if he has no relevance to the main plot? If he's going to be a "side" character then he should still have some connection to the main heroes. But all Daisuke did was appear in random episodes, fight the Worm of the day, and leave again.
Why do you assume that the writers attempted to tie him to the main story? His actor often wasn't even available, leading to that suit-only cameo after his story arc was over, but his presence was required by the main plot. I highly doubt they ever intended to tie him seriously with the main plot.
He had his own stories and some of them were good (like the last one with that worm/woman), so he wasn't a total waste, even if he didn't add anything to the main plot.
When was it ever implied that most of the Worms were wiped out? For all we know they could be hundreds more still in hiding.
Because their leaders gathered a bunch of troops, manipulated by a Tsurugi who wanted to kill them. After that battle we only saw a few of the weak types that couldn't even clock up, with commentaries from various characters about how everything was fine since that battle.
You were saying that he had done nothing before the final battle against the standard worms, I was just giving another example of a participation.
The Hoppers appear out of nowhere, with no real reason for being there at all, to help out the two Riders that still mattered to the plot. How the heck is that meaningful and non-random?
The Hopper's scenes often showed moments about the Hoppers attempting to go back to the "light". That was another of those scenes where they actually attempted to help other people again, rather than just dragging themselves to some meaningless "darkness".
After that episode, Tendo even talked casually with them, something that would never have taken place earlier in the series.
So because the battle was "small-scale" Daisuke isn't needed? Your logic fails me.
Because the battle was small scale, Daisuke's absence wasn't a plot hole or a problem with the construction of the story's internal logic. I'm not saying you must like it.