I grew up in Italy, it really helps with understanding all underlying references to Italian pop culture. The game is simply trying to be as offensive (and blaspheme, most importantly) as possible, and captured a certain common way of thinking within young Italians and the milieu of the internet culture at that point. The game is quite hard at the boss fights, for even Matteo Montesi managed to kick my ass and he's the first boss you encounter.
Most shock games are pretty predictable at this point. You've seen South Park, you've played Postal. That kind of thing is why Eggwife was kinda disappointing, it didn't go any further than I expected it to. Grezzodue is not that. Grezzodue is the first game in a long time that I had to play only after making sure nobody else was home. I am 23 years old and my parents have seen me play postal 2. It's great. It's exactly the kind of dumb shit I would have made if I was 14 and surprisingly good at designing levels. Some of this is lost on me because I'm not Italian but I have played Blood so I understood about 90% of this game I think.