add_filter('nav_menu_item_id', '__return_empty_string');
add_filter('nav_menu_css_class', '__return_empty_array');
add_filter('page_css_class', '__return_empty_array');

The three lines above will remove all IDs and classes from menu items, including classes for the current item. The current item can still be targeted using the aria-current attribute:

.menu li a[aria-current="page"] {
  color: red;
}

Documentation

• developer.wordpress.org/reference/functions/__return_empty_array
• developer.wordpress.org/reference/functions/__return_empty_string
• developer.wordpress.org/reference/hooks/nav_menu_css_class
• developer.wordpress.org/reference/hooks/nav_menu_item_id
• developer.wordpress.org/reference/hooks/page_css_class