Hello,
Our Instructional Design team ran into the same issues you are when project planning for our clients! Our clients were having difficulties with identifying where our bottlenecks were, and why they existed at all (the same "plug and play" mentality was found to be the cause of this).
We found that what helped, was both talking with and demoing the process we went through to build the courses. Once we demoed our design process the reasons why building quality training takes time was made a little more clear. We went into details starting with our Subject Matter Experts, and then moved onto logistics, before finally getting into the details of how and what our course authors do when creating a course.
Sadly, we were never able to create a standardized training material that talked about the design process since we found that different people were confused about different aspects of the entire process. Some were familiar with LMSs, while wholly unfamiliar with how course content worked, and some were the other way around.
Eventually we settled for asking each new client if they were aware of the process and what went into it before starting. If they showed any confusion or gaps in knowledge, we made sure educate and demo until things were more clear.
The only time we received pushback (they weren't happy that it still took a long time), we ended up building two courses as a future example. One course which was dynamic and full of interactions, the other course static and quite bare (but with the same basic information fully intact). We recorded the time required to design and build each type of course, and presented them as options. Seeing the difference and the time required between each really helped to drive home what the extra time was providing, while also giving our client an option to choose a less time-intensive option if they wanted.
I sincerely hope this helps! The world of eLearning is highly complex, and passing that information on rarely easy! Keep at it and good luck. :)
