When did that happen? Have always complained that attachments in Outlook weren't drag/drop unless going to your desktop - rarely could you drag into an app. I only noticed it because I was watching the launch and saw a drag/drop add-in
Interesting, I have Outlook 1903 and a later Teams client, I can not drag drop straight from Outlook.
Are you sure you haven't installed a third party tool like https://www.dragdrop.com/ ?
@Steven Collier I have to apologize - you were absolutely right. I just went through all my downloads and found I installed it back in the middle of January....
Oh well, I can heartly endorse the 3rd party tool - it works great! :)