No civilization harvests 100% of the sunlight that falls on a planet because you'd kill the planet. (Type I)
Nobody is going to build a Dyson sphere around the Sun (Type II) because there is not enough mass even if you cut up the inner planets.
(That's not to say you can't build something really big... Like a habitat with more land area than the Earth.)
It is similarly unthinkable that you'd build a shell around a galaxy. (Type III)
Because people are thinking about this they aren't thinking about more interesting (if impractical) ideas like "Could a civilization smooth out the energy output of a quasar and live off it somehow?"
No civilization harvests 100% of the sunlight that falls on a planet because you'd kill the planet. (Type I)
Nobody is going to build a Dyson sphere around the Sun (Type II) because there is not enough mass even if you cut up the inner planets.
(That's not to say you can't build something really big... Like a habitat with more land area than the Earth.)
It is similarly unthinkable that you'd build a shell around a galaxy. (Type III)
Because people are thinking about this they aren't thinking about more interesting (if impractical) ideas like "Could a civilization smooth out the energy output of a quasar and live off it somehow?"