There is no etiquette. That’s a flawed argument.

The seats are designed the way they are by the airlines. They allow the minimum amount of space for the maximum amount of money.

The airlines could make all seats non-reclining with very little effort. But they would lose money because non-reclining seats would be a dealbreaker to a small but not insignificant number of customers…me for one.

The airlines could also make seats more comfortable and reclinable by allowing more space for each seat. But they would lose money because they would sell less seats.

The seats recline the small amount they do because of the natural equilibrium that the market allows between comfort and profit. End of story.

You peasants arguing about which other peasant is a terrible person are blaming the wrong people.