With all the empty roof space on every building, I don’t think it’s a real space problem
You’re not wrong but neither are you entirely right.
I’ve worked on inverter technology, the system that transforms DC like solar power produces to AC which the national electricy grid uses.
They get more efficient, overall, with larger installations because rather than 100 separate inverter losses for solar on every roof you only have a few large scale inverters to provide power to the grid. Also they can leverage high efficiency high power technologies like Silicon Carbide MOSFETs.
Same thing with solar panels, the bigger they are the more efficient they are at converting light into usable power.
The difference in efficiency, while meaningful still isn’t enough to be worth not doing rooftop solar
But in general you’re right.