I think it is playable,u have some weaknesses on dark squares and a difficulty to develop Bc8,but it is playable.
Sicilian Swiss Cheese Variation


Lol I saw a game where Smyslov won against a master, playing this variation. It looks very anti-positional, but it does restrict white's knight fully.

I've not seen it in that exact position I don't think but have seen it quite a bit with 5.Bd3 rather than 5.Nc3. I've seen Kamsky play it a lot. The basic idea is that if Black is allowed to, he wants to quickly play ...Bg7, ...Ne7, 0-0 and then a quick d7-d5.
With the white bishop already committed to d3, it takes White a bit longer to get Be3/Qd2/Bh6 in as something would have to be done about the N on d4 first. It's probably riskier for Black in the move order you gave. After 5.Bd3 g6, White often continues with 6.c4 to cut across the plan mentioned above.
Can someone explain the ideas of this opening, and why it's not just not really bad for black?
It looks horrific for black, yet it seems to be OK (and it is). Take a look: (and yeah, this is actually a book variation for black in the Sicilian)