Yes, the nihilism points were argued to be a point of comparison against, but his aim was didactic in the political realm. He explores this further and more completely in Demons.
I've also read that Demons expands upon many of the ideas in C&P though I had a bit more trouble getting into it. After hearing about these newer translations though I might have to give one a try.
The most unrealistic thing about his writings is that normal conversations don’t have alternating monologues which each go on for pages. Clearly he’s effectively writing inline dueling essays.
Demons is a little more work to get into, as it takes longer to get going than C&P, but the payoff is well worth the setup.
Unfortunately, there are way too many people in real life who do talk in monologues and rarely let others get a word in edgewise -- especially if they're drunk, but sometimes even when they're perfectly sober.
At least Dostoyevsky's characters have something interesting to say.