Authentication of taxpayer identity by soft credit check is not the only acceptable method for verification.  You can refer to Pub 1345 for a more in-depth discussion.

You may be able to get around the default KBA authentication method by submitting your request as an additional document instead.  Since we don't use DocuSign for the very reasons you cited (as we specialize only in expat and foreign national returns), I am not sure whether or how the rest of the process would meet the NIST requirements.

We have been using Verifyle for a number of years.  A number of national and regional CPA as well as EA organizations partner with them to offer its services to their members.  It is primarily a client portal but it includes Pub 1345 and NIST compliant e-signature function.  Here's the whitepaper they published a few years ago for F.8879 e-signature, based on advice they had received from their legal counsel.

As mentioned previously, at the end of the day, you can always fall back on getting a copy of the wet signature by fax or email, which is perfectly acceptable so long as you have verified your client's identity as required.

It is just how things are and plenty have complained about it.  Unless you consider viable alternatives, nothing is going to change, at least in the intermediate term.