Scientists certainly debate this question, and they find it worthwhile. ENCODE defined function as participating in a biochemical reaction, and by extension this is the definition used by many ID supporters. When we use this definition, about 80% of the human genome has function.
If we define function by “it could lose its function through mutations”, which is the definition preferred by most biologists, then about 10% of the human genome has function.
When using the ENCODE definition, almost any DNA sequence will have function. Random sequence will naturally have sequences that weakly bind transcription factors that results in low level transcription, as one example. This is the definition one has to use in order to claim that a large percentage of the human genome has function.
If you use the definition of function based on sequence conservation then random DNA will rarely have function. You will also find that only 10% of the human genome has function under this definition.
The more restrictive your definition is for function the more junk DNA you find in the human genome.