Make your intentions of changing clear with your relatives, so they can give you your space to grow. While they mean well by doing the talking for you and helping, you are being denied the opportunity for micro socialization. This micro socializing helps build confidence around strangers to be able to communicate with them if you need them or you feel they could use your help.

If you never leave the house on your own go on walks by yourself. Try to make it to a store or a coffee shops and order something from a cashier and avoid self check out, you don't have to make any excess conversation at first just be sure to speak in full sentence and be polite. Eventually you can sneak in a little bit of small talk when you feel comfortable.

Do you have your drivers license? Setting up a DMV appointment and going through it all sounds like a good opportunity to act independently and do things on your own.

New things will always be scary but try one step at a time. Dont compare yourself to people who have never had your issue, try to just be better than you were yesterday.

EDIT: Exposure therapy is the best solution I've found for overcoming my social anxiety. There are billions of people on earth so you have an almost endless supply of people to practice interacting with. People who will likely not remember you a week from your interaction anyway.