Adults learn differently. Adjust your training accordingly.
We're all teachers at one time or another, whether we get in front of a class or not. Every owner, service manager and senior technician has to be a trainer. And, oh boy, it's not an easy job!
Whose fault is it when techs are hard to train? Sure, they're inexperienced. They have a short attention span and are easily distracted. Can you do anything about that? Probably not. What you can do something about is how you teach them. Instead of wishing they were different, in fact, blaming them because they aren't different, how about starting from where they are? There's more than one way to teach.