For what its worth, I too wish that Piriform was more pro-active in their beta development for new releases of macOS and future versions. Being an early adopter and and long time user of CCleaner (MAC & Windows), it's like losing an arm when you cannot use what I consider to be the most important application on my system. I realize its a choice I've made, but I've made that choice because it's important to my business to stay on top of the newer technologies for the benefit of my customers. The majority of the utilities I use have had newer versions available for testing under macOS Sierra for weeks and now that we are on the 7th release of the macOS Sierra, I don't think its an unrealistic expectation to have a version of CCleaner available for BETA.
I encourage them to create an Early Adopters BETA program where nightly versions can be downloaded and tested and only benefits them, having such a vibrant community of people willing to take part in helping them continue their role as the #1 utility for both MAC & Windows.