You beat me to it.

Your job at your workplace is what you were hired for. Yes, that position's requirements and workload may change, but that is to be expected. What should not be expected is for you to do all that and do what your boss is failing to do in their own job.

If you'll have to work extra hard to do your boss' work as well... why aren't you getting paid more? Or why aren't you the boss? It's clearly a sign to look elsewhere for employment, if you're not already.

Unsupportive bosses are a sign of bad culture or that their bosses are likely equally unsupportive or clueless. Cut your losses.