Sorry but will we ever hear any understandable reason for this? Are you planning to shut down Atlas and with this action you prepare the lose as much customers as possible in before?
There is no other reason than that possible - because you basically shut down a huge amount of functionality (and I bet you won’t lower costs). We, as a company who relied on Atlas just feel cheated by you - and that is really sad because we had a really good opinion about MongoDB in general but after that announcement our trust is lost.