My Dad taught me the Machinist trade, the only place I have ever drawn a paycheck from besides our Shop was the two years I had to spend in the Army when I was drafted back in the '60's.
One of the things my Dad taught me from day one, (and I try to instill in the men I teach), is the most important aspect of Machine Shop work is to learn WHY you do things a certain way. You can teach anybody how to do something, it is simply a matter of repetition and following directions. The important thing to learn is WHY you do things. Once you have a general knowledge of why things are done a certain way, you can transfer this knowledge to other aspects of machining, and operation and function of machinery in general.
A while back, a customer asked me to assist in the alignment of a large marine gear to the Propellar Shaft and then the Diesel engine to the gear. This was a 3500 HP set. I not only showed his men how do do the procedure, but explained to them why you needed exact alignment of the output gear flange to the shaft coupling. Why you then aligned the engine to the gear in a certain manner so to allow for heat expansion in the verticle and horizontal. And then why you had to secure it all properly so there was no deflection in any of the criticle parts, and then making sure nothing could move under the normal operation of the vessel.
At my shop, we have no CNC machines. It's not because we would not like them, it's just that the type of work we do simply does not lend it's self to type of work performed on CNC machines.