I'll admit, I didn't realize it was 3 episodes cut together until I read the reviews.
Even more so, I also didn't realize that the original voice actors didn't come to film this failed series.
But I will tell you now. I wasn't all that interested. The animation lacked that fluidity that the first movie had (Especially depth, it's like they ditched the details in each frame,)
Some of the added characters were.... not a good choice. Like that lava pet, why would they need that? I just think they needed an animal companion to sell merchandise and add 'cuteness.' If you're going to add animals, can you make them more... magical, ancient- something that fits that they were trapped underground for 8,000 years.
The world-building wasn't all that impressive as-well, but it makes sense, if it were given more episodes it could of had potential- but as a movie... I swear I watched this when I was way younger and I cannot tell you what I remember from it a decade later. Even watching it now, it's like I've never watched it before.