I think you should first retrieve that user role. See my screenshot because it seems you are not retrieving it correctly (I see a list instead of an object).
Then check is this user role is part of the list of user roles of the user. Then remove that user role from the list if the user should not be an admin. And do make sure that you commit that list to the right account.
Hi Ronald Catersels ,
I have tried as you said and printed a log to check in which process my microflow is working but it is defaultly setting Admin role to user each time it logs in.
Please refer the below microflow and log: