Yes AJ you are right, I am using the Adobe Audience manager as DMP. I have enabled the Adobe Marketing Cloud ID service on my property which serves as landing page and linked the same marketing cloud analytics account to adobe campaign deliveries. So AC cookies are replaced by marketing cloud or analytics cookies.
However I cannot create shared audience as this option is not appearing for me in Adobe Campaign create list option as shown below.

Therefore I was trying to use Adobe ID login for AC to get the above option enabled as mentioned in the post quoted above.