Focusing on self is important but that shouldn't make you self centred. It's just like being proud of yourself is great but pride is not.
Similarly, focusing on self is great because thats how you learn what are your needs and what you deserve. The relationships and interactions are a part of human existence. You cant be like I don't want to talk to anyone in world. Even talking to cashier, saying excuse me when someone in front, booking a cab, ordering your snack, these are all human interactions. You know there are many people who aren't able to do these activities too. You might think it's absurd, but it's just they are too afraid or caring too much about judgement.
Hence, first knowing yourself is important. Respecting yourself and setting your boundaries. When you can accept yourself and be confident about who you are, thats when you can come out of people's opinions and judgements about you.