"Mostly in these case, the order is cancelled or partially the order is delivered if one item is missing and the restaurant calls the admin to provide the partial refund or something."
That's why there should be a choice on what to do if that happened. Let the customer decide onwhat to do if there is unavailable items, not the rider/store/admin.
On being not attentive restaurant owner. Not all resto do the On/Off thing, even do we require it. And adding this solution may help food delivery owners and riders.
PS. As you always saying, not all food delivery business have the same business model.