Hmmmmm.. I don't know if the days of secrets are over. I have things that I reserve for people who I think are ready for them. Over the years I found that if you start showing bells and whistles along with the basic things, the gung ho guyz will all start trying to do the bells and whistles and their basics don't develop... so I try to separate different levels of information to different levels of people. That would be "secrets".
you are probably right, too big a generalisation to hold water. Of course there are things that will be reserved and taught to those that are ready for them, as well as things which are explicitly taught that the student just does not grasp, but with enough practice, a lightbulb moment occurs/can occur. If a lower level student is aware that the higher level student is being taught something, for their grade so to speak, is that a secret? The information is not known but they are aware that they will get it when they are ready.
I completely agree, without the basics in place, it doesn't matter what level of secret / information thats given, there are going to be problems.