This could have been great
I remember playing the demo as a kid, when this just coming out, and being very excited about getting the full game for my birthday; alas, my parents could not find a copy anywhere. As it turns out, it might have been a blessing in disguise.
Diggles has an admittedly interesting premise. Years before Dwarf Fortress, it tasks you with creating a colony of dwarves (or gnomes, depending on translations), meet their needs and fight against other denizens of the deep;
Your goal is to descend in the underworld on a quest from Odin to defeat the mythical wolf Fenris. As you delve deeper, you discover new technologies and new resources advancing from the stone age to a steampunk industrial world.
On paper, it could be a great and quite unique colony builder game, predating many classics of the genere. In practice, it's a soul-crushingly boring slog as your dwarves - held back by atrocious AI and general incompetence, will ignore obvious tasks in favour of traveling all the way across the map for a low-priority delivery; they will starve because they fail to realize that they should eat food when hungry; they will change profession back and forth accomplishing nothing for days.
Even when you can wrangle your Diggles into doing something useful, tasks often take forever, as even the most efficiently-built mountain home will force you to ferry resources across long distances just to allow a crafter to sloooowly do their job.
Bottom line, even though the game technically has complex mechanics (the unique experience system, the work turn assignments, the tech progression, the various unique setpieces found in each level) this is a BORING game.
Yes, some mods exist to improve the quality of life somewhat, and while you can (well, must) use console commands to fix a few of its problems, there's no escaping how long and dull this game is. It might have been revolutionary in its day, instead it became a cautionary tale of how bad pacing can ruin an otherwise good game.