What you buy is a preference, and there’s nothing wrong with having preferences. Everyone is entitled to them of course. And there is no reason to shame others for their preferences.
But they are not a good expression of your identity. There’s a difference between buying something to aid your hobby - and buying a consumerist product because you were marketed to. The distinction is hard to measure, but it’s there.
This doesn’t seem controversial, but thinking through it demands many changes of your life. You have to be sure that most things you buy are something you truly want. Maybe you could imagine if you really wanted it before hearing bout it?
To be clear, there is nothing wrong with buying things. Neither is there anything wrong with having preferences between different products. The mistake is in taking it to an extreme – where you find yourself substituting your identity into the things you choose to buy and own.
But things are hollow. They are useless independent of us. And so the causal flow of meaning must come from you. You own a fountain pen because you enjoy writing and how it feels. But you are not a fan of fountain pens because you own one, you are a fan because of your enjoyment.
Take stock and watch for those disgusting motives: which seek to turn you over and cater to needs you don’t even have.