The MacBook is for those people who want an ultra-light portable with a retina display and care about nothing else
That's fair. Which IMHO is very similar to what the Air was like 7 years ago. The Air when it came out was all about thinner and lighter. The iPad's big distinction was thinner and lighter. I don't like Apple's obsession with thin and light but I have to admit it seems to be something people really really like.
You're basically getting an $899 MacBook Air with a retina display. Now, again, I won't short change the retina display, but that's pretty much the only thing that is "better" about the MacBook. Everything else is either worse or equal.
Ye you are getting: thinner, lighter and retina we agree. I should say, even though I don't care much about thin and light, retina, I know from experience, matters a lot I do think that's worth the price difference. Now that I've used retina I'd pay double for it. I spend a lot of time looking at the screen having it be extra sharp makes computing much more pleasant. I can imagine that the weight and size of the macbook might be getting down to the level where you can carry it around in a binder. Business cards, pen, pad for quick notes, and computer when I need to do something detailed. That's a nice setup. Might even be worth enough to get me to go back to a desktop + laptop setup. I've been thinking about a iPad + keyboard for much the same reason.
OTOH f I still have to carry a bag then they can add an extra pound or two and I don't care. Certainly I think the Mac Pro is the far far better computer. Apple is offering genuine choice. One person wants a Mac but can't afford so they go with the Air. If thin and light matters a ton, the MacBook becomes a no brainer. If thin and light is important, and retina is important but neither is critical then the person has a choice Air vs. Macbook. If they need ports Air vs. Pro....