I find this post to be particularly honest and I would like to state that I respect all of the views you have presented here (before I respectfully disagree).
To say that shows from the past were more entertaining is a subjective statement. How were they any more or less entertaining than shows of this day and age? According to your post, this would be due to the inclusion of more recognizable music and themes, which again is extremely subjective. A tune that brings back great memories and is very familar to one person may be completely foreign to another. And while I love hearing renditions of songs I know and love, I also enjoy lots of abstract music (both in drum corps and my other musical tastes). Just because a show does not present "familar" material, does not mean it has failed to "entertain" members of the audience. Which brings me to another point. As I am a relative newbie to drum corps (first discovered it in 2000 as a high school sophmore), I was never aware of the corps' "obligation" to "entertain" the audience. I was simply amazed at what I was witnessing on the field! It was like marching band, but on crack! Performed at a level that I had always imagined, but never thought possible! Not until I talked to some older fans at a few shows and started reading rants on the internet did i realize that not everyone shared my awe. However, to me it never mattered if a corps played music I was familar with or if a show wasn't full of melodic music. If I liked the music and the corps performed what I believed to be a well designed show at an incredible level, nothing else was important. I still hold these views to this day.
Moving on, you state that the Cadets shows of the past couple years have supressed the talent of the corps members. I will interpret this as a complaint about narration, however, please correct me if I am wrong. In 2005 and 2006, there is simply not enough vocalization to cover up the corps. I say vocalization because I do not consider a few seconds of voice blurbs to be narration, whether it is amplified or not. In 2007 and 2008 however, the narration is a considerable part of the show. I can completely understand why folks do not like the narration. I was weary at first as well, but have since embraced it. It does not distract me, it does not "cover up" the corps in my opinion, it does not reduce the corps to playing supportive long tones in my opinion. I enjoy listening to the 2007 and 2008 shows both with and without narration -- I feel that it works equally well either way. While some music is more "background" oriented, I feel that this does not compromise the compositional quality of the music. Next, I will agree, the narration in 2007 was not literary genius... however, I firmly believe that the narration and music were staged appropriately, having a natural ebb and flow feel. This to me is grounds for innovation. The logistical integration of narration that satisfies both voice and music equally, must come first -- the well-written prose will come later.
My long winded point is that, although the "entertainment" has stopped for you, it continues for many (not all, but many). I do not think that corps members would be driven to such high levels of performance if they did not ardently believe in both the current state of the activity and the organizations they willingly choose to seek participation in. If a few spoken words and some different music ruin that for you, I feel sorry for you. To me, drum corps is music -- all music, not just something familar. To me, drum corps is motion -- not just symmetrical designs and rigid movement, but also all kinds of crazy shapes. To me, drum corps is art -- and to stifle it by trying to define what it "is" and "isn't" is never good.
I know not everyone can open up to change, as the past holds some wonderful memories and feelings, but it never hurts to try...
**edited for grammar**