No it's not HMRC's fail. They've successfully used the Government Gateway for about 17 years now. They don't need GOV.UK Verify (RIP).
It's GDS's fail. GOV.UK Verify (RIP) offers HMRC nothing – 60% of attempts by the public to use it fail and it can't handle companies and partnerships and trusts, both of which would make it hard to collect tax.
Biting the hand that feeds IT
