Hello,

I am checking Appearance > Widgets > Shop page widgets area. I see Product attribute filters and no Category widget.

Here is the options provided by the Category widget http://prntscr.com/mlwrm5 there is no option to show categories only as this widget does it. Filter attribute will never show any categories.

More information about Woocommerce widgets https://docs.woocommerce.com/document/woocommerce-widgets/

Best Regards