I like Dyson Spheres/Swarms in concept. Is it possible on paper, yes. Is if feasible to accomplish? No. Not even a little bit, imo.

Any Dyson sphere or even swarm would demand an unfathomable amount of resources, time, and manpower. It would be a mega project that would take thousands of years. You’d need to totally disassemble a cosmic body like Mercury or the Moon to even have enough materials. Even with wildly more advanced tech, you’d end up using an incredible amount of energy to build this, and the EROI would take hundreds more years to ever come to fruition after it’s completed.

I’m of the opinion that any civilization advanced enough to theoretically build such a megastructure has likely figured out a much more feasible energy source by that point.