What's wrong with...fiberglass? It's not like the 'glass used on a 'Vette today is the same stuff your dad used to patch holes in his tri-hull boat. It's a woven honeycomb material that is as light as aluminum. Only thing that will go lighter is a carbon fiber weave (which is...get this...a carbon fiberglass...).
Aluminum sucks.
Seriously. It sucks.
You think your steel bodied car gets door dings now. Wait until someone rams a lumber cart into it at full speed at Home Depot. And then you get the damn bill. The only thing more expensive than aluminum is repairing aluminum. Ford has driven the cost down on its trucks, close to that of steel, by basically making it such that almost every panel can be replaced, as opposed to repaired. This makes some types of damage (e.g., hail) cheaper to repair. But not all types. And insurance database records are showing about 10% more body damage claims on F-150s for 2015+ vehicles, compared to those before. Not compelling data overall.
Ferrari choosing to use aluminum means nothing in the world of mass produced cars. Let's be clear, there are more Corvettes produced every year, than the entire line of Ferraris like 2-3x as many Corvettes as Ferraris. As a result, there are definitely more repairs conducted, more miles driven, more racetrack events, etc. A Corvette in aluminum would not only suck to repair, but it would likely be considerably more expensive, since GM would have to re-engineer it, like Ford did the F150 to keep repair costs down. Either do that or just start selling 10k units a year like Ferrari does and charge Ferrari prices...
Oh and it wouldn't weigh any less...In fact it would probably weigh more. This reminds me a bit of "metal framed" gun discussions. The only real reason to pick aluminum over polymer is because there isn't a polymer frame to choose. Otherwise your choices are polymer or steel. Steel for weight, polymer for not weight. Structurally they're about the same. Unlike aluminum, which even in handguns, sucks, compared to plastic or steel.