Im not sure which of your many comments to respond to here but we certainly have learned that a small part of "junk" DNA (as that term was originally meant) performs useful functions not directly related to protein coding. So the comment you replied to is absolutely accurate.

Of course you are accurate as well: if we subtract the protein coding and the known non-coding but useful bits the rest is almost certainly absolute junk... duplications, bits of retroviruses, etc. But it would be inappropriate to claim we are absolutely certain none of it is useful. Will we find out 50% is useful? Obviously not. But I would rather say "current evidence suggests at least 97% is true junk; we are not likely to find large sequences with hidden uses at this point".