You aren’t subsidizing McDonalds labor cost. If McDonalds paid them more, they would be paying more than the revenue that’s attributable to them, and creating a net loss by hiring them and they simply wouldn’t do it.
As a society we have decided that people deserve a livable wage. That is a good thing. Minimum wage laws are a distorting way to accomplish this because they put a cost that should be borne by society (no-skill workers should have a livable wage) and force it on industries that employ workers with no skills. Subsidizing the income through government transfers is frankly a more equitable means of achieving that goal.
That being said, in such a regime however minimum wage laws are necessary, not because McDonalds is exploring the workers, but because they are likely to exploit the government.