If that's correct, that only makes it a much less interesting idea at the recent circumstances. But as soon as these circumstances change, MMT gives an important insight in the constraints of governmental spending.   (The real resources, available in the economy and not the deficit)

"In general, wealthier people are able to take more risks than poorer people (utility functions are more linear at higher wealth). Altruists represent these poorer people (this point is more relevant to global health and development than animal welfare and long-term future), so should be sensitive to undiversifiable risks. In other words, I don't think it's obvious that we should be more patient (I'm talking in general terms, not about the specifics of economic conditions right now)."

I think there is a mistake in here. I suppose that the utility function of altruist is even more linear than the utility function of wealthy people. This is because the return in utility units for every poor individual we (as altruists) are donating to declines really strong but there are so many poor individuals (at least yet) that the good we can do is an almost linear function of the amount of money we can spend, so altruists should be nearly risk neutral. 

Despite this, I agree that it is not obvious that we should more patient.