You forgot "customized", and order drinks before food too - separately. The other part is: I dislike touching a phone screen while eating, so it needs to accommodate that too.
Edit: on a 2nd thought - how would family order look like - the kids need some way to link their orders (albeit having phones) to the payment. You'd need a temp password/pin for everyone to link to?
The ones paying the check are the ones making the orders. Makes splitting the check a solved problem by default. If it is a family with kids making the order, the kids simply pick what they want (no linking required for just browsing the menu), tell the parent what they want, and the parents order from their device. I don't think it is a hard necessity for everyone ordering stuff by themselves. Whoever pays the final bill can handle actually ordering the food.
At some point kids like independence... at least to choose/read the menu - around 5-6y of age. It'd mean sharing the phone with them one by one, instead of having a menu each.
Normally I'd pay the bill entirely (split whatever is non-issue at all) - however picking items for everyone is just bizarre, e.g. everyone would have to tell what to order, I would have to find and not mess up - in short not fun at all, cosplaying the waiting staff
Probably for US there is a market, but here in Europe restaurants mostly have a facebook page and that's it. They mostly don't really have an online presence and they don't really care either. That's what high taxes do, penalizing high achievers so ultimately every service 'stops' at a good-enough level.
