Sovereignty isn’t about complete control. It’s about borders. When we say a country is sovereign, we don’t mean it can do anything it wants vis ‘a vis other countries. Only that it controls what happens within its border. Outside its border, it must interact with others as peers.
So too with SSI. The big idea of SSI is that if gives the individual a place to stand as a peer instead of having to be within someone else administrative identity system where they set all the rules. SSI allows people to interact with other people and organizations as peers.
for more on why I think this leads to better relationship and a few — dare I say it?? — generative use cases that arise from those better relationships.