If you make a certain set of highly unrealistic assumptions about what "sustainable" requires, yes.

If you look at how human history has actually gone, you find that doomsayers in every time could find trends that, if projected out forever into the future, looked "unsustainable". And of course, if those trends had continued as they were, it would not have been sustainable. But the trends never continued as they were.

We humans can adapt to change by changing how we do things. Claims that our current population, or indeed any current human activity, is "unsustainable" ignore that crucial fact.