California has access to all the West Coast trade-ports between the US and China. With these ports in place, we don't need to rust-belt states to ship-in goods. An our economy is centered information technology and entertainment, so we don't really need to worry about reduction of economically viable exported goods (all farmed and manufactured products will be consumed internally, thus bolstering that aspect of the California economy).

Also it wouldn't be morally correct, because California isn't a singular Democrat state. The coastal districts are Democrat, everything else votes Republican. Cecession would create exactly the same problem in California as we have right now: a massive rift between two parties.