Can't connect to current iPhone (7) without adapter.
Can't use iPhone 7 Lightning headphones without another adapter.
Can't plug in camera cards without adapter.
External monitors will need a another new adapter.
Can't connect just about anything you already own without an adapter (mouse, keyboard, USB drives/devices/printers).
Costs much more than before.
Let's start with what I agree with you about:
The Lightning headphones -- not only can you not connect without an adapter, NO ADAPTER EXISTS!
I agree it might have been too soon to pull the SD card slot, especially since there appears to be plenty of room for it.
As for the rest, this has always been the case with Apple that buying the next generation Macs required eliminating most, if not all of the previous gear. So I don't really see this as a problem. It's just part of owning a Mac.
But with respect to the charging cable, I think Apple made the right choice. To put this into perspective:
The iPhone 7 is going to sell over 200 million iPhone 7, not to mention the over half-a-billion Lightning devices already out there the same cable can be used with.
Apple will likely sell around 20 million Macs, all together, this year -- not just the new USB-C models. Compared to the installed base of maybe 100 million, maybe 10% of all Macs sold by the end of the year will have USB-C only ports. So that works out to be something like 2% of all iOS users may be using a USB-C Mac by the time the next iPhone comes out.
So instead of Apple supplying them with a cable on the less than 2% chance they will buy a new Mac, they continued to supply the vast majority of customers a cable that will be most useful in all of the environments they may encounter throughout their day.
I don't disagree that supplying a $4 adapter from USB-A to USB-C with the MacBook would have eased the transition, but I also don't agree with Apple supplying adapters in the first place. I think including a 3.5mm adapter with the iPhone 7 was a mistake, especially now that the AirPods have been delayed since it encourages people to keep using old 3.5mm equipment.
With the MBP, it might encourage people to keep using cheap adapters (which could lead to other problems) rather than buying the correct cables and equipment for the new MBP.