Sigh,that's a difficult one...
I will start with what's wrong (that's always easy )
- I see that the performance is far too low. FOV is unacceptably short. You need to make it much higher, sight range increased like 3-5 times. When you do it you most likely will notice it all crawl to like 1 FPS I'm afraid... That's the first thing, because if you can't make it fast enough nothing else matters. That's what my programmer's nose tells me (Irrlicht + Bullet Physics + Minecraft destructible terrain are not possible to work fast enough on nowadays machines, note that even Minecraft, which is far less complicated technically, is not running properly on 32bit systems).
- inconsistent technology, sometimes the gameview is smooth, but but when you destroy things it turns out to be made of cubes. It's not good aestetically, nor gameplay wise nor technology wise. Everything ther looks incompatible, like you tossed together all kind of cutting edge technologies disregarding if these work together or not. To put it shorter, are you making a traditional FPS or a cube based destructible terrain game or voxel based non limited to cubes destructible game. You need to choose one
What to do (the harder part):
- first, I would throw away the current engine (I know, it's radical). But my hunch is you have fallen in love with it (what kind of programmer would not, there are such cute things included!). You should have fallen in love with the game not with the engine. In the end it will hurt your game. Besides it can't be salvaged without cutting out huge parts of it anyway.
- make a decision what kind of game you are making and stick to it (you can even arbitrarily choose it randomly). Would it be an RPG, action, strategy? Or maybe mix of these? If yes in what proportions? What would you put on the box, on which shelf in the game store the game would land? Again, it's not that important which one you choose as long as you choose one. The safest bet is to choose a kind of genre you like the best. (I also suggest making a list of games you like as aplayer and posting it here, we might be able to help you more then)
- make a decision what kind of technology you want to use (as above, traditional FPS engine, cube engine like Minecraft, some vexel+physics engine maybe)
- generally, I would sit down with your team and discuss, what kind of games you all liked to play, what kind you always dreamed to make etc (without trying to fit it to your current game)
Once you have answer to these, post them, the discussion will be better focused then.
I also need to note that I have to disagree with most what others above wrote. These things are about polish or secondary things. But these alone won't help you. Only the core gameplay an save it (and only after the core is fun you can worry about polish and interface and art, you can't polish something that is broken in its core). Once you have the core gameplay forged out you can attempt polish.