A heroic/over-the-top performance by Karloff and a couple of fun meta jokes are not enough to make this flick consistently entertaining, not to mention the poor monster design and ridiculous plot holes like an eyeless monster who has no trouble finding its victims.
I have been looking to watch this movie for a long time. It's a solid action/adventure story with distinctive animation style, but is lacking in character. Not sure I have much idea of who Tin Tin is other than journalist/adventurer. It also has a weirdly anticlimactic end intended to set up a sequel instead of closing the story properly. Still, a mostly enjoyable watch.