Yeah if you didn't like Titan Quest that might be a problem

All things aside, Grim Dawn is the game's spiritual successor and copied over most of TQ's game mechanics refined into something a bit more stream lined and balanced (for a single player game).
TQ had the problem that many class combos were just not worth it (especially once you reached legendary difficulty). Grim Dawn has largely avoided this. Though it only has 6 classes right now, all them have great synergies and potential pairs with the other five. The new devotion system also helps with filling in gaps in a build (it's structured a lot like Skyrim's skill trees) The game still has set maps, though some objectives/entrances/target enemies move around the map, so while the map stays the same, you'll usually find slightly varied paths through some of the dungeons (it took me three runs of the first dungeon to notice though). The maps are a bit more open now with more to explore and endgame has been expanded with crafting, new 'nemesis' bosses, and a few other time sinks but it's still a fairly grindy game. The Victorianesque art and aesthetic is a lot nicer, bit of a Lovecraftian feel, especially as you go further into the game. That is really where the changes end. Grim Dawn is the game TQ fans wanted; TQ II under another name.
That said if you didn't like Titan Quest I can honestly say I don't think Grim Dawn offers much to change that experience