Portable digital identities are still an unsolved problem, even with Nostr.
They take a step forward in portability by using public keys, but that comes with a step backwards in multiple other dimensions like being able to recover your identity, key rotation, and just general ease of account maintenance.
I think Nostr is an important step in the right direction, but won’t be suitable for general use until those issues are addressed, and addressing them might require more drastic changes than simply adding an additional layer on top of it.
Age is only a protected class if you are 40 or older.