Teams and Office and SharePoint and Loop are all Microsoft products. They're all integrated tightly with Teams.
That's what they mean by interoperability within the walled garden of Microsoft products.
Sorry but creating a meeting in teams is almost completely disjointed from the equivalent process on Outlook. Half of the features are missing on the Teams side. I can't even see other people's calendar or add people from my contact list outside of the org. It's terribly integrated.
I think that's your organizations settings. I have virtually the same process to make a meeting in Teams as I do in Outlook. Both are easy. I can definitely add anyone from my contact list, including those outside of my org.
I wasn't commenting on the quality of these integrations. They're shit and I know it. Just pointing out that integration does mean something here
And those integrations would be perhaps less shit if they had competition showing them how to/incentivizing them to do it better.