Project Wallace is a reasonably priced online service you can use for continuously assessing your CSS’s quality, much like tools exist to make statistics based judgements on other code. The core tech is fully open source though. Hence you might start assessing your own statistics (it’s not judging (yet)) by executing the highest level command line tool: wallace https://murb.nl (it (murb.nl) is bad, I know, too many just not exactly equal font-sizes, many id-selectors, the style was more than 7 years ago).
If you want to improve on your score, you could self integrate the output of Constyble in your CI-pipeline, which allows you to write simple targets for your css’ quality.
While you should never let statistics dictate quality, it is a great starter to find areas to improve upon.