Software is written and tested to run on operating systems available at the time of release. There have been 3 new versions of InDesign released since CS6, which was already at the end of its life cycle three years ago. If you want to run old software you need to understand that hardware and operating systems change over time, and Apple in particular doesn't care a whit about their customers and maintaining backward compatibility. There is no financial incentive or justification for Adobe to patch obsolete products to run on new systems.
CS6 is almost four years old. Adobe has been saying for several years that there would be no new updates to CS6 to support future operating systems. It's not supported for Yosemite or El Capitan (or for Windows 10 for that matter) because those operating systems (with all their changes) happened after the release of CS6.
Adobe and those of us in this forum who answer questions have been saying that you'll only keep up-to-date by getting a Creative Cloud subscription. Sorry for that, but it's just the way it works.
Actually, I think Yosemite was safe (though I don’t know what the official cut off was) so it’s probably the latest you’ll want to try running CS6 on.
The real issues started with El Capitan.
There were some minor problems with Yosemite and CS6 but most people didn't encounter them or could ignore them. No longer with El Capitan.
The only one I remember was the photos thing.
So what you're trying to tell me is that Apple doesn't care?
That's correct. They have a long history of not caring.
Peter is correct. Apple has never placed a priority on backward compatibility.
That of course carries some advantages but for anyone wanting to run old software; well, here we are.
I've certainly had better customer service experiences with them than I seem to be having here. Even on products that were out of warranty. Here I'm being told that a product that I've had for three years is technically obsolete. I can't believe it would be that hard or that expensive for Adobe to come up with a patch.
And since I've been researching it lately, it seems that InDesign in particular has had quite a long history with this type of problem. There are posts of people not being able to open CS3 on startup. Not just in Mac but also in Windows. So it's hard to view this as an "Apple only" issue.
As per Adobe addressing backward compatibility, I can count the number of times I had to deal with not being able to open a file that had been saved in CS6 from the CS5 version. I've never really understood why Adobe insisted on rending anything that had been saved in the more recent version unusable in an earlier version unless you took the extra steps to save it as a file that could be read in an earlier version.
To your last point, with each version ID has added new features (at user request), and the internal data structure of the files has changed. Pretty hard to make an older program understand the new data structure.
I was able to get InDesign to open after trying various things. I'll provide some information in case it might help someone who's having the same issues.
I'm working on an older model Macbook Pro unibody.
Things that didn't work/didn't affect my situation:
1) trashing the two InDesign preference and cache files didn't seem to affect anything. There is another way to trash the preferences. You start the program then immediately press 4 keys simultaneously: SHIFT + CONTROL + ALT/OPTION + COMMAND (you should get a pop-up asking if you want to delete the preferences).
2) Java. I had already installed the legacy Java 6 runtime because I was getting messages about it in Photoshop and Illustrator. If you need that, you can find it here:
Also, if you can't downgrade because you've installed a Java upgrade, there's a video about it here:
The thing that worked:
Creating a new user account in Mac System Preferences. For some reason I can run InDesign (seemingly without issues so far) from the new account.
If someone doesn't know how to set up a new account, there are instructions for it here: