For parents who suck at parenting, is it only right for me to do most of it?

I'm 17, and I have two little brothers. There's Dad and Mum. Basically, infinite freedom in this house. Cursing all the time, fighting, watching whatever on TV, eating all the time, disrespect, you know every possible thing they could do to misbehave they do. Parents let this slide, they are depressed about it, but they just basically "run away" from it. They'd rather give in, than to deal with the problem. So, I basically fill that gap in. I limit them to things, I make sure they do things they're supposed to do, and I make sure they don't do things they're not supposed to do, I'm not bossy, but I tell them what to do, if there's something they need to do. And, I discipline them, I don't beat them up at all by the way. But, they need to see someone's not scared of them, and they have to be kept in line to a certain degree, I mean it can get out of control. So, I'm doing the right thing, and this is good? What do you think of it?