[Question] How do most utilitarians feel about “replacement” thought experiments?

In this paper, Simon Knutsson discusses an objection to standard utilitarianism: that it endorses killing many (or all) existing people if that leads to their replacement by beings with higher utility. For example, he lays out the following thought experiment:

Suboptimal Earth: Someone can kill all humans or all sentient beings on Earth and replace us with new sentient beings such as genetically modified biological beings, brains in vats, or sentient machines. The new beings could come into existence on Earth or elsewhere. The future sum of well-being would thereby become (possibly only slightly) greater. Traditional utilitarianism implies that it would be right to kill and replace everyone.

People who identify as utilitarians, do you bite the bullet on such cases? And what is the distribution of opinions amongst academic philosophers who subscribe to utilitarianism?