There's hardly any motivation to keep playing after the main story is complete (thereby making the game quite short) and it doesn't help that the difficulty hits a massive spike right at that point. The various gameplay styles are also hit or miss. But perhaps the worst thing of all is that the story doesn't involve Undergrounders, which is like 50% of the series's charm.

EDIT: After revisiting the game I've started to realize how much it is bad and I hate it. All the menus from the title screen to the world map to the attraction specific screens are outright terrible not to mention slow. The concierge that greets you at every attraction is super obnoxious, always making me instantly regret deciding to get back into the action. What's more is that this screen doesn't even seem to lay out clearly (if at all) whether you actually completed the attraction, only whether you've attempted it. (meaning, it will display your best score, but that doesn't tell you much, since that score could have been a failed run.) I am absolutely repelled from playing the game any further. I've begun to strongly suspect that the game was never actually good, but happened to be easy enough so that there wasn't much stopping me from breezing through the main story before the flaws and lack of charm began to take their toll.

I like Mr. Driller, but this entry is not a good example of it. I'm honestly shocked by this because I always assumed this one to be the holy grail of the series.