If you reversed all shadows and gradients, wouldn't your active control's lighting become completely inconsistent with the rest of your interface? Or did I misunderstand?

But you're right that flat design takes away some of these tools. That's why it's important to look at each situation as its own thing.

For example, a big call-to-action button on a homepage cannot be toggled and lives by itself, so making it flat works. On the other hand, making an "on/off" toggle flat can potentially create a lot of ambiguity.

But even then, it's up to the designer to find workarounds and new solutions, such as http://drbl.in/giHY