Tex has unprecedented backwards-compatibility. Microsoft does pretty well too. Adobe is a mixed bag. Calling it "almost unprecedented" is simply dishonest.

My 30-year-old Photoshop files used PostScript fonts. Even multiple master fonts, which don't have the same broad support as mainstream PS fonts.

Good luck opening them with Photoshop.

Truth be told, most of my 30-year-old files are in PageMaker.

InDesign has some support for them for a while, but dropped support. Adobe's official line is "Open the PageMaker files in Indesign CS6 or an earlier version first, and then save them to native Indesign Format (.indd ). Once the files are saved in InDesign format, Indesign can open the files."

Of course, Adobe won't sell you old versions of InDesign to do that with, so YMMV.

I dropped Adobe for Affinity not so much for price, but because I can buy the software and use it forever. Even when I retire. I still have an Adobe subscription (paid for by someone else), but I don't use it.