Can confirm that your confirmation of M3DB being cancelled is incorrect and is actively being worked on at Uber and elsewhere.

I do agree there were definitely projects that were overly ambitious and optimistic that likely that should have been better planned. I think you are weighted firmly at one end of the spectrum however. I have some obvious bias being involved in one of the projects you outlined, but I still think you are blindly covering a swathe of projects in one go without any nuance at all.