"Advanced civilization go really advanced, to a point their activities would be undetectable to us or would appear to us the nature of reality itself."

This is science fiction, not an argument. We have no rational reason at the moment to believe this is the case, or even possible.

What we do in fact have is an increasing trend towards efficiency. Projecting that out along crazy growth curves suggests that advanced aliens are likely to be more horrified by such a waste of negentropy than we are. What can we do with that much negentropy? Nothing, basically. What can they do? Simulate many millions/billions/whoknows of human-level civilizations?

They're not more likely to be indifferent about such waste, they're more likely to prosecute you, for mass civilizational murder.

I've often thought that if civilization could advance to that point in the future, that I'd have a difficult time explaining to my great-great-great-X grandchildren that when ol' great-great-great-X-grandpa was young, you know, pouring a tank of gasoline into the car got me from point A to point B and that was it, despite it being enough energy in that one tank of gas to, say, simulate an entire human's life time. Well, kids, we didn't have that option! The tech didn't exist. So stop trying to put ol' Greats on trial for things he couldn't control, OK?