Microsoft needs to prioritize this request and work on pushing this feature in the upcoming release. This is a major part of the Information Governance strategy that we develop with our clients where we educate and train them on the best use case for using the right components within M365 to achieve better compliance and productivity. This is by moving records or long-term business productivity information in the email to one of the group repositories like SharePoint or Teams for long-term storage preservation, retention, and group collaboration. Users are not going to buy in if every time they have to toggle the 'New Outlook' button to drag emails or attachments that they want to move to the group areas. For some clients, the option to switch to the previous version may not be even available if it is pushed to everyone's throat via GPO