To be fair, I think that's pretty respectable, especially in this day and age – and particularly given its price and class. A Ferrari 296 GTS, which has a list price of some three times the C8 Z06, comes in at around 1,600kg (~3,530lb) on the road, if not more, so for the bigger and far less expensive C8 to come in near that is good going. Doubly so considering that, say, an old C4 ZR-1 would clock in at around 3,400lb on corner scales.
Sure, lighter is better when it comes to outright performance, but the C8's a substantial and well-equipped sports car, like many of its competitors. And times change, too; many modern cars are remarkable at concealing their weight, and there are lots of factors that make it difficult for that weight to be easily cut down – safety structures and equipment, interior equipment, emissions equipment, increased engine output that necessitates larger and heavier braking, steering, suspension and cooling components and supporting systems, etc.
Even a new Lotus Emira is probably getting on for 1,500kg (~3,300), at the kerb...