That "function keys can do anything" is, in my opinion, the exact reason they had to go. They're scary for the typical user. What is F7? You may know, but it's not obvious in any way. That some of them cause destructive actions (e.g. Alt+F4 on Windows) makes it worse - they're scary to many users. And even when after figuring out what some of them do, one is stuck wondering "was that F8? Or F9? Oh! It was F10" (which, includes the worry that a wrong guess could cause problems).
Though, I cannot believe they shipped it without the haptic feedback to make it clear that a button was actually clicked.
^ Also, none of that, to me, includes Esc. Esc seems clear enough in its intent, and I hold no ill-will toward the Esc key.