I'm not very good at this game but I don't really need to be to feel good, which I feel is often a good test for this type of game.
While I cannot say much for the gameplay, I will say it has the best secrets in any FPS game because the reward for finding some of them is entire genre subversion. Within its engine is a fishing simulator, crash bandicoot platformer and a fucking dating sim of all things.

A hilarious and passionate love letter to doom. Now how the fuck do I beat Penis?