There must be plenty of not-so-young people who don't have a credit card or passport.
Edit: the article says "Adults would be forced to enter personal information like passport or credit card details", so I guess other forms of ID with a date of birth would be accepted.
The government already have a GOV.UK Verify programme for identity assurance that they want to be funded by the private sector. They'll presumably just encourage people to use one of those private operators (currently Digidentity and Post Office) and maybe it'll encourage more operators to spring up.
They screwed up that for me. I registered, worked with it for a few months (via Expedia, iirc), then they just said "sorry, we're disabling this for you" - probably because of Brexit, but who knows. Can I recover my account somehow? Who knows, I couldn't be arsed and just let my accountant do things for me.
Edit: the article says "Adults would be forced to enter personal information like passport or credit card details", so I guess other forms of ID with a date of birth would be accepted.