As far as I'm concerned, I don't give a single damn about the fact that the current cars weigh over 700 kg, including driver. I do care about the fact that these things are so long nowadays due to the regulations and therefore need the material and thus weight to remain safe for the driver and perform at the maximum level demanded of the cars.
I see people complain about the ever increasing weight yet few are blasting about the fact that these heavyweights are, at least in practice, the fastest F1 cars ever, period.
I really wonder what the outcries over here would be if all of a sudden the cars are regulated to be a full meter shorter than they are right now, turn out to be some 50 kgs or so lighter but also slower than the current freightliners.
The current cars are also that heavy because of being so long and thus needing the material to built it up but also, because of their tremendous speeds and the trememdous levels of aero grip generated, the lengthy backbone of the car needs even more material to beef the backbone up in order to remain as stiff as possible and not deformate under the stress of these aero forces...