yes, the SSPI is failing because RC4-HMAC is turned off by the Registry key. So the question is how to make this work without using a protocol that is deemed unsecure by about everyone in the world.
As I see it, this is more of a feature request than an issue.
In Windows environment the Connect-VIServer cmdlet has been using the SSPI mechanism provided by the OS.
Since it is deemed insecure, that SSPI mechanism is disabled by many.
So it will not work anymore.
And there is no solution to still provide SSPI and avoid the insecure mechanism afaik.
The same is true when you run that same Connect-VIServer on other platforms than Windows.
I would suggest to launch a new idea for this request on the PowerCLI Ideas site.