A lack of food has never stopped me drinking, and presumably you were still able to consume non-alcoholic beverages which is an upgrade from Y in itself now.

If push had come to shove, you could have bought from the BoB menu and submitted the receipts to BA for reimbursement. They would most likely still have thrown some Avios your way as compensation for the service failure and effective meal downgrade, maybe still the 5k if you'd fought hard enough.

I do think your expectation is somewhat unrealistic here, and excessive compensation in the past caused by BA simply backing down to such requests has led to the unsatisfactory position we have now.