WordPress cannot override files other than template files which reside in the root directory of the theme. Looks like the function override check is missing here. But for shortcodes, if you need to modify the content or presentation, we recommend you create a new shortcode (like [my_team_slider]) of your own in the child theme and copy the code from the parent theme shortcode function (in this case mo_team_slider_shortcode() – rename and use in your child theme for your shortcode) and customize the same. Effectively same thing as overriding the current shortcode function. Hope this is clear.