You’re telling me a toggleable panel that flips when it needs to is too expensive? You’re already installing the panels. You’re already doing all that. The only difference is the material on the back side of the panel and of course some sort of crank and shaft to rotate it.
Or if only there was some sort of powered component that could rotate it when it reached the capacity you know since the name of the game is power
In addition to what allero said, you seem to only be considering future installations rather than existing ones. Retrofitting existing equipment is massively more expensive than changing a design prior to building it.
Solar panels are very cheap, and any modification, even just a moving cover, greatly ramps up prices. No, really.
We just need a lot of panels to generate significant amounts of electricity, which would necessitate a large cover or a lot of mechanisms - which would get expensive on that scale.