InDesign CS6 has reached end of life and will never be updated.
Illy and PS are engineered differently and Adobe were able to update those for retina display. InDesign required a ground up re-write which was accomplished with Creative Cloud.
If this this the only issue you're having with a new Mac consider yourself fortunate as many haven't been able to get it to run at all on El Capitan or Sierra.
indesign CS6 was never updated for retina screens, unfortunately. nor will it be.
Indesign CS6 runs perfectly well on Retina iMacs. It seems to just be the laptops that have this blurry issue.
Indesign CS6 also runs brilliantly with MacOS Sierra - it's extremely fast and the minor glitches we used to see occasionally with El Capitan seem to have gone away.
So while it may have reached end-of-life for Adobe's purposes there's still plenty of life left in it, and there's STILL no compelling reason to move to CC.
if it still runs ok for you, i agree completely.
Before I purchased my current MacBook Pro 13" Retina, I had to try InDesign CS6 to see if I could work with the blurriness everybody was talking about. Due to software protection, it was not easy to find a reseller that could install his copy of ID to let me try.
In the end, I found the issue to be really minor for me. I didn't find it blurry, but just less refined. It was not as if I was looking at something out of focus. Just an outdated UI, but still very workable.