Login.gov is a fine authentication service, but cannot deliver the identity assurance level (IAL-2) required to identify people. (It may not be able to deliver AAL-2 authentication soon either as standard evolve.) Uploading a picture of your drivers license is not a meaningful validation of your identity.
The reaction of the Senators here is the equivalent of “I’m shocked to hear there is gambling happening here”. Typical pandering. Literally every drivers license and ID in the country is running through a biometric identity provider run by a contractor to identity duplicate licenses. Many DMVs outsource credential production to a third party.
I don’t think ID.me is the best solution, but it is better than providing a trivially stolen number “what was your AGI last year” that facilitates billions of dollars of fraud annually.