Yes, this is what Diablo3 would have looked like (had it been released in 2006) - but this cannot be a bad thing. This is a beautiful game that goes well beyond being an eye-candy.
Titan Quest offers quite realistic graphics achieved even on medium range PCs (a 5-year old system I used to have with only its video card upgraded to a nVIDIA 7600GT, can run it easily with everything on high). I particularly liked that you can see the exact armor and weapons on your opponents and, after you killed them. Fighting a hard opponent is rewarding because everything drops for looting.
I am a great fun of AD&D RPGs. However, in Titan Quest (and its expansion) there is no deep background - except lots of excellent Mythology (correctly told for once). Sure, there is no "official 20-sided dice" getting thrown somewhere in the background - but do you really care?
Hack, slash, zap, burn and destroy. Loot, sell, buy and equip. Repeat as needed, until satiated.
You will surely enjoy it! A game that is is great to look at and great fun to play.