Thanks for posting this, made me realize I have that error message also.
I’m currently running ads (made a week ago) that have placement as a utm param, and they are tracking accurately today in Google Analytics. Looks like they won’t let you create new ads with these params though.
Maybe this is part of the IOS14 changes. Not certain.
Following iOS14 and changes to Facebook off the back of it, it will no longer be possible to segment reports by gender, age, placement. Makes sense that this would impact the dynamic placement tagging too