@grigione I’m glad it got solved and perhaps you have a higher score in GTmetrix and Google PageSpeed Insights. Note that Asset CleanUp deals with whole CSS files, not just part of them. The file that you mentioned is generated by WP Rocket from existing loaded files. Some of those files have CSS that might not be needed on the homepage (or whatever page you were referring to).
For instance, you could have a file that only needs 60% of its code on the homepage and the other 40% is unused. If you want to have a file on the homepage like style-homepage.css that would load only 60%, it’s technically possible, but you need to spend some time building it via tools such as Google Coverage which shows you which CSS is used and which not for the window size that you loaded. Note that for mobile it could be a different story. You need to make sure everything is good there as well.
It’s time-consuming to strip it and you need loads of testing this way and it’s only worth it if you have a huge amount of traffic and the time/budget to hire a developer to do it. I would not worry about it for now. It’s not really worth it if the unused CSS is not large that will significantly impact the total page size.
