In my opinion CES is something you benchmark across your own experiences so you can hopefully find a high effort experience to focus on. Also I am sure it varies wildly by industry and experience. In order to benchmark CES you would need to match industry and experience. That being said your company can set what your acceptable threshold is for CES.

I second the above comment. It also depends what standard you're using. My company used to use the Gartner question design with 7 agree/disagree scale points with top 3 box as the score, and were benchmarking against Gartner's numbers. I changed to easy/difficult scale with just top 2 box included in the score. So it's difficult to say what the benchmark should be between various companies that may not align to how you're asking the question to begin with, and to add the differences with industries on top of that takes you even further away from being able to compare yourself against others.
Currently, we set a goal for ourselves of reaching 80% Extremely Easy/Easy, and are just benchmarking against our own prior year scores and are trying to push our ratings YoY.