I, too, am sorry that we cannot use the new N7 in the old dock. And that there is not the opportunity to have a similarly functioning dock for the new N7.
The great thing about the (late) 2012 dock was that it allowed you to plug in an audio jack and leave it plugged in.
This means much less wear and tear on the Nexus 7's own headphone jack. I use my dock in the kitchen and it is permanently hooked up to a cheap old pair of computer speakers. That means that I can listen to podcasts when I am pottering about in the kitchen and also charge the unit at the same time.
When I use the N7 in the car I just use a regular miniplug into my car stereo aux input and recently I've noticed occasional problems with the headphone jack on the N7. One channel drops out. It is remedied by giving the N7 a gentle squeeze on the right edge. This tells me that the hardware is starting to deteriorate. Imagine how much worse it might be if I had been plugging and unplugging a line every time I used the N7 in the house!
I also like the angle at which the N7 stands in the dock. It makes it easy to look at the screen when I have it docked. I can look up recipes, glance at notifications as they come in, etc.
I do have one of the "folio" type covers (3rd party, not Google) and I cannot us it in the "standing" mode. The N7 just falls over onto its face when I try.
Yes, the dock was too expensive. Yes, it was unconscionably late, But I think it's a great pity that we've gone backwards on this issue.