I have been using (and loving) MS Teams for some time now. But I have been using OneNote for eons (as the best app MS have ever made, in my opinion).
The problem is they do not (at least not on a Mac) talk to each other.
In the new 'unified' system of Teams, planner, and tasks being integrated, we need to have OneNote link into that too. Onenote has a tag for 'to do' so it would make logical sense that creating this 'to do' in OneNote was import into our todo, task, or/and planner tools too.
If the new todo feature is looking to import tasks from todo, and planner/teams, then it must include OneNote also to be useful.
In the windows environment creating a OneNote todo used to (i can't vouch if it still does) create a task in outlook. This doesn't happen in the mac environment. So a OneNote todo is an isolated tag. The only way of using this is to copy/paste (which is inefficient) or use OneNote search by tag - which detaches this todo's from the rest of O365.
+1 to @PaulB175 's request. I'm just learning how to use Teams with the goal of finding out if I want to push my division to switch to Teams. If all of the features are not truly integrated, I'm going to keep being unpleasantly surprised and not sold on why we shouldn't just manage work through email and OneDrive.