I think it does need improvement, but it's up to you if you are going to improve or not. Missing color for the text, keep using $menu_dropdown_text_color so if its value is black and for the offcanvas background you choose a dark color, the color will definitely disappear or have no contrast. For menu links in hover state keep using $menu_dropdown_text_hover_color, which depending on the color would happen the same as with the text color, you must use $offcanvas_menu_active_menu_item_color or create a new one for hover.

I also think that these colors for offcanvas should be present in all presets and preset.xml to be able to use it directly without inheriting dropdown colors.

Regards