With five main parts to the ADDIE model, implementation makes up only one part. I find is key that only one-fifth of the ISD model is actual content delivery. The majority of time is spent on analyzing, creating, designing, assessing, and evaluating what will be or has been taught, and this makes sense especially in my own classroom. As a teacher, I have seen the units, where I implemented each piece of the ADDIE model, meet objectives without problem. I have also seen lessons fail that were mostly implementation and weak in the rest of the rest of the areas of the model. When I follow ADDIE, I see better results from my teaching.
For the last three years I have been working on and evolving a poetry unit I do with my students. I have spent months on my own and with with colleagues planning, developing and tweaking this unit. And each year I continue to improve on it. Last year I analyzed their final test results and saw that there were some weaknesses in the unit and students did not have enough opportunity to practice identifying some of the elements of poetry. I went back to those sections and taught them in a different way, created a new assessment and saw huge improvement. Not only did my students meet the objective I planned, but I still have parents from last year that approach me and thank me for getting their students to love poetry (a desired byproduct). I strongly rely on academic research to shape my instruction, but it is my own personal success with using the ADDIE model that confirms its validity in my mind. I cannot deny what I have seen with my own students.