There's a simpler reason for the lack of an Ethernet port. Compare the size of an Ethernet port to a USB port on the Mac Pro and then look at the side of your MacBook Pro. The Ethernet port would not even fit.
I bought a 2012 MacBook Pro (which Apple still sells in stores) instead of a 2015 model partly because it still has an Ethernet port. Apple could definitely make laptops with Ethernet, they're just choosing not to in their desire for ever thinner machines.
I also feel the keyboard and trackpad quality has deteriorated on the thinner devices. I much prefer the snap of the click on the 2012 MacBook Pro trackpad to the Force Touch simulated click.
I've seen expandable Ethernet ports on several ultrabooks - Toshibas in particular. They spring closed when not in use and the bottom half expands when you need to plug in a cable. Apple could manage it tastefully, I'm sure.
