Basic Authentication and Exchange Online – June 2021 Update

Our organisation would gladly migrate it's email provisioning and mailbox management tools from using Basic Auth if we could get the OAuth2 method working effectively.  Our testing indicates that the remote PS we need to use is unworkable using the new connectivity method with certificate thumbprint owing to connection delays and possibly general slow response.  In many cases the connection delay for each action is up by an order of magnitude over basic auth.  This results in a terrible user experience and in most cases of complex / repeated actions, actual timeouts which break the processes.  We have heard (somewhere) that Graph API is being updated to have more  mailbox functionality added which will apparently work much better.  Hopefully when we see this it will allow functionality equivalent to PS get-mailbox, Get-MailboxStatistics, Get/Add/Remove-MailboxPermission etc? 

Does anyone have any indication of what the timeline is for either an improvement in connectivity speed for thumbprint connection or a  suitable extension to Graph API?