The epitome of sadness in the direction of PC gaming.
So don't buy games that are essentially created for multiplayer. I personally don't see a problem - you usually know what you are buying before you actually purchase it. This game was obviously marketed for its MP. But it does also have very fun coop zombie horde survival.
If you want SP games - buy those, the game is the same on the xbox though so I don't know how the SP campaign is the epitome of anything regarding PC gaming specifically.
Metro 2033 is a better choice if you want an SP fps, there are plenty out there - this just isn't one of them. Or some of the MoH series (although unsure on the newest one - i think it is basically MP too).
Personally I only played through the first 2 levels of the SP to adjust my settings and get back into the feel of the game. I never even started SP in MW2, not even the first level.