There is no consensus yet on the biological function of dreaming, and neither is it clear if suspension of reflective self awareness is necessary to perform those functions.

What is for certain: even in lucid dreams, physiologically you are still asleep, and in genuine REM sleep. So in that sense it should provide the exact same restorative and cognitive benefits. It's just that several brain regions associated with self awareness, metacognition, attention, and cognitive control show increased activity.

So taking that into account, I would argue lucid dreaming only has net benefits, if you value those metacognitive features.