Apple's only mistake with the new Air, IMO, is not keeping the old keyboard. I'm right on the verge of needing a new laptop and I'm eagerly looking at a MacBook Air 2018; the keyboard gives me pause, just because it's different than what I'm used to. But the Air name alone, the form factor, and how it's built is basically perfect for me. It does everything I need and then some without making me wait.
As to which you should be choosing though...that is a tough one. The MBP line doesn't feel as unique as it used to, as the price point is just too high for me to justify it to anyone, and the low-end MBPs are basically just heavier MacBook Airs.
(I wouldn't be surprised to see a new keyboard design roll out across some Mac laptops as early as this year, but if it does, it won't come to the Air for a while. Also, I wouldn't be surprised if the new design is still optimized for extreme thinness.)
It's also wonderful that when I need a new machine it's just $350.
Most people still have usb a peripherals, so the laptop situation is confusing. I do podcasting and had to advise someone in the industry on the i/o of new macbooks, it's not obvious for most.
Because as a 12" MB user who'd like some 2019 performance, I can't think of any other good reason.
The iPad lineup to me doesn't seem particularly confusing at all, other than perhaps the naming. There's pretty clear differentiation across the products and price points. I'll be honest, I think some of your questions are deliberately overstated; I think Apple expects "non-tech people" aren't ripping their hair out over the difference between Lighting and USB-C, because they look at the charging cable that came with their new iThing and can pretty easily figure out which end goes into the iThing and which end goes into the wall socket. Most people don't connect their iPads to their MacBooks. Most people shrug at the weird naming. These are mostly tech pundit problems. I would love it if the MacBook lineup could be as clear and non-stupid as the iPad lineup again.
I think it's appropriate to ask whether this would've happened under Steve.
There are certainly things Apple has done in the last five years that make me ask that question, from the Touchbar to the butterfly keyboard to the way iOS's text editing controls, especially with external keyboards, are still shit compared to the Mac after nearly a decade. "But the Air is thicker!" is...just not one of them.