What's the benefit of this over a passport? A passport is a physical thing, so you don't need to have a phone to be able to use it, proves who you are with the same details as this digital ID, and will probably require a similar amount of paperwork to get hold of
You usually don't want to carry a passport with you at all times. In some European countries (e.g., the Nordics), you have your ID, driver’s license, firearm license, etc., all in a government app that can be verified with an app used by officials. You can also sign and authenticate all paperwork with the same system
I would trust the Nordic governments to write an app to put on my phone and not slurp up all my data and spy on me with it. I can't say the same about the British government