I just completed a reasonably advanced course on computational biology and I was still taught that although we have found noncoding DNA performing functions, the majority of our DNA is both noncoding and not used for anything (i.e. evolutionarily obsolete, transposons, etc).
You are correct. Most non-coding DNA is junk, which amounts to around 90% of the genome. Dead transposons alone make up just under half of the human genome.
I just completed a reasonably advanced course on computational biology and I was still taught that although we have found noncoding DNA performing functions, the majority of our DNA is both noncoding and not used for anything (i.e. evolutionarily obsolete, transposons, etc).