No one is paying you. You are not obligated to do or say anything simply because you are a fan of a group.
Don't enjoy a song? Then don't listen to it. Don't have room in the budget to buy an album? Enjoy the extra space in your home that not having a collection gives you. Don't feel like streaming? Listen whenever and however you want. It's all good.
You don't have to defend or promote a song you think is bad. You don't have to watch every members' fancams if you are only interested in one. You don't have to have to force yourself to have the same level of excitement for anything and everything your faves do.
Just don't crap on the members or other people's parades. Be respectful. And if you're a fan, try to be open-minded and give changes and new things a chance before making a decision. After that tho, the decision is up to you.
I hope everybody finds something that brings them joy in kpop.