There seems to be a fair amount of perpetual confusion over just what migration entails and what questions qualify. It seems to me that a bit of rephrasing would reduce that confusion considerably with very minimal effort.
At present, the menu item for canned migration paths (flagged or voted) reads "This question belongs on another site in the Stack Exchange network". But that's not really correct. Simply belonging on another site is in no way a reason to consider a question off-topic, because many sites can and do overlap in topic scope. Rather, the question must be a) off-topic and b) fit another site's topic scope [and c) not be otherwise close-worthy on the target site]. So the current phrasing helps promote the misconception.
Let's adjust it, like this:
This question will be well-received only on another site in the Stack Exchange network
The two changes are both key. Mentioning a good reception (and not merely "belonging", as though we're attempting to file all our questions into the appropriate pigeonholes) can help avoid migrating junk. And emphasizing the exclusive nature of the migration avoids the silly "well, you can ask this question here, but it might be slightly better over there" closures.
Merely changing the text may not be enough in the long run to salvage Mary Ann, but at least we can improve things for a while until a more permanent solution is found. (One such solution is basically an amplified version of this, requiring much more dev effort but reaping greater UI clarity rewards.)