So here is the thing I don't get, if we think of Dyson Spheres.
Imagine Earth is like a pea, and sun is like a basketball. The pea is 30m away from the basketball. Now imagine you were to draw lines from the basketball to every direction. And infinitesimally tiny fraction of those lines hit the pea. In other words, a tiny, tiny fraction of sun's energy even reaches earth.
Mankind's total energy need in our current state of development is 18 TW. The total amount of solar energy reaching earth is 174,000 TW. So even if we could capture all of the tiny fraction of solar energy hitting one planet, we'd have 10,000 times more juice than we do currently. What could we do that we can't do now if we had ten thousand times the available energy at our disposal? It's hard to think of anything that would require that much power.
Now, up the game from there to all of sun's output, a total of 3.8 x 10^26 W, or 380,000,000,000,000,000,000,000,000 W. That's about a trillion times more that wll the sunlight earth receives in total, and about a quadrillion times more than all of mankind uses currently. What would a civilization do with that amount of energy?
What if they're much bigger than us, like dinosaur size? They would need much more energy than us for their 1000" screen tv's