This story is tragic, it should end tragic, Walt broken, batterd and ultimately destroyed.
Pretty sure this 21st century television show set in New Mexico doesn't have to conform to Shakespearean genre structures if Vince Gilligan doesn't want it to.
Plus this work is at such a scale it doesn't really need to deal in having a "moral" at the end. It'd be kind of contrary to the whole project if what Vince Gilligan intended for people to take away from it was "being a murderous meth kingpin is bad"--fucking obviously it is.