They really needed to make Decade a full series....
I don't think it's a matter of not being a full series.
Unlike some people who complain about Decade, he isn't just saying that there was no story or something. He clearly got the story... and just disliked it.
Even if there had been more time to execute it better, he probably still would dislike that conclusion.
Another thing I didn't get is what in the hell Narutaki was(did I get his name right?) was he shocker, or what the hell?
Narutaki was someone who seemingly hated Decade from his Dai-Shocker days (considering how he goes all "told you so" in All Riders). We don't know why he hates him specifically though.
He wasn't a Shocker member originally. Tsukasa pretty much says that he only joined them because he hates him so much and the Zol disguise disappears after he's hit. It wasn't the first time Narutaki teamed up with monsters either.
I really think that movie that was first advertised would have been better as a conclusion than the one we got.
It'd probably have been just a longer version of the movie that we got. Go back to the last episode, even in the original version, Narutaki talks about Decade killing every Rider and then dying himself. The main plot never changed.
Some details like Natsumi facing Decade, Yuusuke's brainwashing not getting randomly ignored and Tackle (who originally had a subplot about Stronger's death in Tsukasa's hands) would probably have been handled better with a longer running time originally intended (Decade vs All Riders was supposed to be a double feature, not part of a 3 episode thing), but I don't think it'd be significantly different from what we saw, at least, as far as the main plot goes.
The teaser didn't mention it, but Shocker remnants were mentioned in very early texts about the movie. Kiva-la's identity also was confirmed to be Natsumi in one of the magazines still talking about the original movie. The "true world" was just the "true form of the Rider War World" according to some of the side texts too, and still was in the final movie (the changed wallpaper), just completely irrelevant to anything...
Basically, I don't think the original ending was substantially different from what we got. Specific details and the execution might have changed, but the outline, which is what really irritates people, would be the same.
The only great advantage might have been Other Tsukasa or Narutaki as a possible final antagonist, rather than random encounter Doras. Although even the promotion for The Last Story initially still talked about Narutaki having a great combat power... but I guess they couldn't finish whatever monster suit he was supposed to get on time and just dropped that idea.
It seemed like each writer that wrote for this "fanservice series" didn't try to make any effort in some way to work with each other to add consistency throughout the series to make it appear like they were trying to build a story for this "anniversary series."
But they didn't, and the end result was basically.....Aikawa wrote his episodes based on HIS INTERPRETATION OF DECADE, Kobayashi wrote her episodes based on HER INTERPRETATION OF DECADE (and more Den-O spam), Inoue wrote his episodes based on HIS INTERPRETATION OF DECADE, and Yonemura did the same as everyone else.....but worse.
Neither writer in the Decade writing staff appeared to not wanna work with each other, so we just got a messy plot as well as a messy execution of a messy plot.
Only if you have no attention spam. Rewatch the first episodes. Most of the stuff hinted at there WAS fulfilled later on. Decade had a very clear direction aside from the All Riders vs Decade / The Last Story mess up. It just was a direction that didn't please most fans in the end. Although, considering the comments from producer Shirakura before and during the series, that's not really surprising.