This has been possible for ages now.
https://support.wix.com/en/article/editing-your-member-signup-settings-for-the-default-form
Just make up your own custom signup and login lightboxes, then you can add whatever you want to be collected on your signup page as well as the email and password.
If you do go down that route then you must set your signup settings to suit it too.
https://support.wix.com/en/article/corvid-enabling-custom-site-registration
Otherwise just use the custom signup form that Wix has provided through Wix Forms for you to customise.
https://support.wix.com/en/article/about-the-member-signup-form#custom-signup-form-1