Yes, this is true of OAuth, which is exactly what the latest Model context protocol is using.. What's the concern again?
I guess maybe you are saying the onus is NOT on the MCP server but on the authorization server.
Anyway while technically true this is mostly just distracting because:
1. in my experience the resource server and the authorization server are almost always maintained by the same company -- Jira/Atlassian being an example
2. the resource server still minimally has the responsibility of identifying and integrating with some authorization server, and *someone* has to be the authorization server, so I'm not sure deferring the responsibility to that unidentified party is a strong defense against the critique anyway. The strong defense is: of course the MCP server should have these responsibilities.