I remembered watching this a few years ago as a six year old child in the early 2000s when it first came out and I actually liked it. Which is why I think that this surpasses both "The Time of the Great Giving" and "The Secret of Saurus Rock" as the best of the series.
Yes, the story's a little episodic filled with forgettable songs and the fact that it's too short, but it doesn't matter.
The animation is very nice to look at and the editing is very decent. The characters are well-developed and the pacing moves along very nicely. I know it's weird, but I actually liked the villains. Rinkus and Sierra were great, but I think that Pterano steals the show. Littlefoot was tolerable as the main protagonist as is the two rainbowfaces.
The strongest aspect is the excellent voice acting and the hilarious dialog. I like Sierra's "No, no, no, jeb, jeb, jeb, it's driving me nuts nuts nuts!" and the rest of the quotes in this movie. The voice acting, like I said before, is very excellent with Michael York stealing the show for portraying Pterano very well.
Overall, not excellent, but is arguably the best in the series and it's definitely worth watching!