I'll speak as someone who has been on both ends of a drawing.
I've done my own cad work - I've taken the basic, intermediate, and advanced classes at the local CC. Nice classes, 2 nights a week for 10 or 12 weeks, etc. Also took Pro-E just to learn what it does. I think that has been very helpful throughout my career.
I also had 4 years of hand drafting in high school, before CAD. I think learning those basics - what an isometric view is, how to project lines, how dimensions should be called out, etc. - should be mandatory for certain disciplines, especially structural engineering.
I've worked in estimating and I've worked with installers and I've seen bad drawings. The more you know about how things fit together (or don't...) and how to convey that on paper to another human, the better you become as an engineer.