https://docs.moodle.org/30/en/User_profiles

I have been trying to do this in Moodle 3

Preventing users from customizing their profile page

By default, users can customize their public profile page and add blocks. To prevent this

1. Go to Administration > Site administration > Users > Permissions > Define roles
2. Edit the authenticated user role and untick the capability moodle/user:manageownblocks