The two use cases suggested:

Alice holds a digital wallet that securely manages her identity, data, and authorizations for external apps and connections. Alice uses her wallet to sign in to a new decentralized social media app. Because Alice has connected to the app with her decentralized identity, she does not need to create a profile, and all the connections, relationships, and posts she creates through the app are stored with her, in her decentralized web node. Now Alice can switch apps whenever she wants, taking her social persona with her.

• Creating a profile takes what, 2 minutes? And you do it only once per app.
• Connections and relationships: Okay so you want to copy your list of followers? That’s nothing remotely new. Pleroma literally has that (also for blocks and mutes).
• If you want automatic discovery of existing followers, fine, but note that already exists on some platforms via email addresses or phone numbers. All you’d need to extend it to secure, decentralized identifiers is for those platforms to have a metadata field for users to put such an identifier. Hardly revolutionary.

Bob is a music lover and hates having his personal data locked to a single vendor. It forces him to regurgitate his playlists and songs over and over again across different music apps. Thankfully there’s a way out of this maze of vendor-locked silos: Bob can keep this data in his decentralized web node. This way Bob is able to grant any music app access to his settings and preferences, enabling him to take his personalized music experience wherever he chooses.

So you want to import playlists between music apps? That could only work if each song has a globally unique identifier for the playlists which is known to all the platforms. That isn’t the case, and changing that would require every musician to change their workflow.