Flying Bull - you may have seen a video called 'Children of the Magenta' - it describes one of the problems with reliance on automation, specifically the type of scenario you mention.
This is where the pre-planned FMS route is suddenly changed (by ATC instruction for example) - instead of adjusting the flightpath simply by hand, the crew go heads in and start punching buttons - often with some delay to the required route change, and often degrading lookout significantly.
Some of us oldies converted to glass cockpit quite easily and find the automation easy to manage, knowing you can always 'fly-through' if the computer doesn't do what you wanted it to do (or does the wrong thing you asked it to do in error
)
Sas - I always assume I will make mistakes and make allowances for it!