An error occurred while saving the commentMike Black commented
I would also like to upvote this as an issue. We are currently engaged in a major project to move legacy on-premise SharePoint sites to our SharePoint Online tenant. Given the current focus and emphasis by Microsoft on the Modern Experience, I would agree with others who have posted comments on this issue. We as a company and an E3 license MS customer have embraced the new Modern Experience and are moving sites into that mode. Microsoft needs to continue focusing on completing the transition to the Modern Experience so it's SharePoint Online customers do not have to continue to have this mixture of the classic and modern experience in SharePoint Online sites.
We are happy to share that we are actively working on it. We will be sharing more details about the plans at the SharePoint conference in Vegas.
Here is the MS road map item
Here’s the session we’ll share more details.