Necessities
I don’t see anything wrong with buying “shit you don’t need.” There are lots of things that I don’t need, but which I choose to buy anyway because it makes my life better to have them. E.g., books, music, tasty food, computer equipment, furniture, hot running water, trips to visit my family and friends, etc. etc. etc. Of course, I could choose to abstain from these and limit my spending only to necessities. But why should I?
Of course, there are also many activities that make your life worthwhile that do not require a purchase. To the extent that corporatism cuts people off from these forms of enjoyment, corporate capitalism should be undermined and resisted. But whether or not one chooses to personally abstain from spending on non-necessities does just about nothing to address these issues. The power of corporate capitalism to restrict alternative forms of enjoyment has very little to do with individual decisions about consumption and a lot to do with the monopolistic privileges granted by State power at the points of production and acquisition of land and resources. These are better resisted through labor organizing, targeted strikes and boycotts, resistance to State coercion, etc., rather than doing what “anti-consumerist” groups typically do, i.e. adopting an ascetic lifestyle and chiding, ridiculing or harassing those who aren’t as personally hardcore as you are.