Did you read my post? I said no doctrine is being changed. What he is doing is proceeding, through an executive action, to change the practice in such a way that marriage is not insoluble - without having to “proclaim” anything.
Then you follow it up with: without having to get into the messy question of the fact that you can’t change it. Not even if you’re the Pope.
Which is a contradiction. either He is changing it or he is not, If you believe that he is changing it then please tell me what doctrine he is changing.