I understand that the drop down navigation functionality is part of the responsive design
Not specifically. It’s just part of the general design. Lots of non-responsive themes have dropdown navigation menus too. Are you using a child theme? Only category pages are not listed in the primary menu by default.
I have created a child theme, and so far the only difference between my child theme and the rest of the site are simple styling changes.
So how do I remove the drop down functionality?
Are you using a custom menu?
Then how are you adding category links to the menu? Can we see this site?
By creating pages and placing them in the parent of the main navigational section.
So these aren’t category pages but pages of posts, yes? Again, can we see this site?
These are pages, that a child-pages of parent pages. I can’t show the site because of security purposes.