I'm still to finish my first game, and i doubt it will be a blockbuster. I think one error was hyping your first game too much, and going directly for steam greenlight. I doubt it's as bad as some people say but here's a few pointers on how i would have gone about.
* Make a small concept game, based on the same mechanics. Maybe even one small level. Investing too many hours on a big game, THEN getting negative feedback would dissapoint anyone.
* Even before release... get constructive feedback from alpha and beta testers. Take pointers, try to improve some parts.
* Release it for free, for fun, and learn from the feedback.
Although it's a great achievment just to finish a game.... your FIRST game! Even if it didn't turn out to be a great game it's still would give you a lot of insight in how to produce a game from start to finish, where a lot of people fail and give up somewhere along the line. I can tell there's a lot of effort put in to this, but some people don't see it that.
I have tons of asset creation to do myself, but before I even start on it my main focus right now is to finish ONE level, with a few assets, some even placeholders, and run a lot of playtests with friends to get feedback. I'm expecting things like -> The controls doesn't feel right, it would be cool if you did this&that, etc etc.
I don't know how your workflow was during the production, but feedback, and feedback early is better than feedback late when you're done with the game. I would also focus on some part or mechanics of my game and do it REALLY well. So what if the game has shitty graphics if it plays really well, and is fun to play, or so what if it's a bit clunky but it's amazingly beautiful and has a nice atmosphere.
Anyway. I would probably not give up, since u certainly have what it takes to make a game from start to finish and have it released, market it, you should start planning for DARKBASE 02 or a new title, and make it even better than the first one, based on the feedback.