I’m not quite sure how you mean it’s using the parent style.css….technically it should be when using a child theme. However, you should not be copying over the complete CSS from the parent into the child style.css file. Only copy over the parts you want to modify.
Based on your example, you would not be deleting the drop shadow…instead you would modify it to be:
**The content-wrapper has no shadow, it’s actually the one I did above as an example.