You're right, it's not true that all sorts of utilitarianism require aggregation of vN-M utility functions. That was an imprecise statement on my part. However, as far as I can tell, any sort of utilitarianism requires comparing, adding, or averaging of some measure of utility across individuals, and I'm not aware of any such measure for which this is more meaningful than for the vN-M utility functions. (If you know of any examples, I'd be curious to hear them.)