Thanks for the ticket number, Dutchbird.
I surely understand the frustration. I try to avoid having that social media echo chamber syndrome. Any long-term user like you knows problems happen and typically get sorted out. All of them, sadly not. But I'm sure OCIO as a framework and ACES as a Color Management system will have attention.
The color shifts happen mostly based on color and gamut compression, when large color spaces and high dynamics move into small formats, like REC 709 or sRGB. This will not change; with any new ACES version, new shifts will happen going into smaller formats.
One reason is that the renderings have no IDT (Input Device Transform), and if everyone has his/her outcome from a render, then the Tonmapping and Gamutcompression for smaller formats will have very different outcomes. Think of an S-Curve in Photoshop; while moving the underlying content up and down in exposure, the midtones might move closer to the shoulder or the toe of the S curve, which will change things. This is, in a nutshell, why the REC709 or sRGB RRT/ODT has shifted.
New solutions have been announced, and one of my many ACES trainings (since 2012, I have taken ACES classes all over the place) showed last year a new way to handle this. (color.training is the URL; I'm an alumnus of the Color Academy for Professional Colorists) Dado, the Color Academy owner, trained us with these new tools back then.
In short, things will continue to change. Hence, renderings should be stored in ACES AP-0 and 32bit/channel float.)
All the best
