Good manners
The dining table as a place of learning
Waiting until everyone is there. Not speaking with a full mouth. Passing the bowl on before taking more yourself. At the dining table all of this comes together, and for a small child that is a great many tasks at once.
This is why I think it makes sense to take on one single thing per week. This week we are practising passing the bowl. A child with one goal is proud when it succeeds. A child measured against ten things at the same time gives up.
And one more point that matters to me: the table is not the place for lessons while the food is being eaten. Short reminders are enough. The conversation about rules is better held before or afterwards, so that the meal remains a good moment.