Concur that service quality has significantly decreased since the early days. I own an S and X, both purchased new. The 2013 S was delivered at Rockville MD and the 2016 X was delivered at Tysons Corner VA. I also agree that the app, while not "worthless", is much less than "useful." And it is not possible to get anyone to answer a phone or answer an email -- if you can even obtain an email address.
I just had my S in for some maintenance --- include a charging issue that, in my opinion, Tesla refuses to address --- they say it is "normal" or my battery just needs to be rebalanced. I explain all that I've done and it's like I'm talking to the wall.
And look at this photo --- it is my Model S after returning home from the most recent service about two weeks ago. I always walk around the car when I pick it up to note any damage. But I don't open the frunk --- after all, why should I? I returned home -- fortunately only about 5 miles away from the SC -- and opened the frunk in order to replace the things I normally carry there. All interior frunk trim was missing! In addition, there were two part boxes inside -- one was a pyro fuse and the other was a fuse holder of some sort. I'm not sure, but there might have been some thought that parts of my battery / charging system needing repairs, so these parts were ordered. But then it seems they decided my car was "normal". Anyway, I had to drive back to the SC. And of course, you can't speak with anyone because all the doors are locked due to coronavirus distancing. I tried using the web link to contact them, but it simply sent an auto-responde saying that my car service was complete and I could pick it up. I finally found a technician moving a car into the parking lot and I showed him the frunk, and asked if someone could come and fix it. It took them 20 minutes or so to even acknowledge me. While they put everything back in place, no one could answer my question about (1) why they still don't believe the battery/charging system is not working correctly; and (2) why (why why why why) would a service technician close the frunk and NOT see that parts were missing?