What is the problem with receiving orders from a higher authority? That's what kings and their ilk do, and it happens all the time in games, and stories, and real life. Besides, being told to do something doesn't mean you have to do it, so agency is preserved.
This got me thinking.
Is the DM presenting an end of the world scenario agency denying?
The players (and the PCs) CAN refuse, but if the DM then follows through - it's likely the end of the campaign.
Sure the DM can have "others" save the world instead, but after that happens a few times, it's basically the DM crying wolf.