I would offer that Web3 assumes that there are digital identities owned by the user, typically by proving control of a private key.
It doesn't really solve any of the traditional usability problems of maintaining a private key, which is why so many users end up just signing up for a website that will handle it for them.
Specifically the issues that come to mind are key recovery and rotation.
What amount of personal hardware resources does a person need in order to have "full control?"
Is there a way to guarantee that a user maintains "full control" over their identity as opposed to having it be stored on a 3rd party site?
What would a 3rd party site that is operating less than trustworthy (a not uncommon situation in the web3 world) way be able to do with an identity that they hold in trust for someone who doesn't possess the consistent access to the previously mentioned hardware resources?
If your only computing device is your phone and someone steals it, do you lose your identity?
In the event that your house burnt down and all of your computing resources have been destroyed, is there a way to attest to be able to recover your identity?
In the event that your evil twin decides to burn down your house, what mechanisms exist to prevent them from claiming your identity?
"Full control" by being forced to engage with a protocol they never designed in order to authenticate their own existence? That sounds more like full submission to me.
It doesn't really solve any of the traditional usability problems of maintaining a private key, which is why so many users end up just signing up for a website that will handle it for them.
Specifically the issues that come to mind are key recovery and rotation.