Defining what is really good and bad is a very hard thing to do, and has been the subject of philosophical debate for millennia. It gets really hard when we try to construct a reasonable logical foundation for ethics, but then we always check it by comparing it to the intuitive ethics in our evolved/cultured meat brains. Of course, the intuitive ethics always "wins" and we conclude that the problem must not be there, but any conflicts must be problems with the ethical framework!

So you can conclude that you should just do whatever makes you feel good and all ethics are nonsense as you seem to prefer, but I'm not sure that you've really refuted the basic premise that you should try to maximize the amount of good you can accomplish.