I too must say that getting a product done and out the door is an achievement in itself.
Getting the sh*t kicked out of you on steam/youtube/anywhere else with end customer exposure is to be expected, to some degree. Even successful (game and other media things I worked on) products will attract a lot of bile.
On the other hand, if you strip away all the hating and fuming and "this game is so bad my grandmother died from it"-BS of the adolescents are posting, there might still be a lesson to be learned about the scope, depth and challenge people expect from a game.
I've read through a few of the comments and reviews, it seems that some people are seriously unhappy with the performance (which is of course partially out of your control, C2 exports with their browser engine coming along is quite fickle on weak systems, as you probably best know yourself), but other than that, the critique seems to center around enemy patterns and behaviours.
And that is something one could work on in the next product. In my opinion you should let it cool off a bit and not quit, but put all you've learned from this experience to good use.