Other than hiring 5K new people to do nothing every day but read every single post and comment and downvote them into hidden posts?
Not a thing. Spam is a plague that really can not be eliminated. I have no idea on percentages but I am sure the vast majority of spam is simply bot automated. So they can pump out as much as they want whenever they want. Create as many free accounts as they need and proceed. Yes RC will help combat spam but will not eliminate it. The big accounts that can do this have far more RC than they need and will have no problems spinning up new accounts, delegating enough SP and letting loose the army, if they so choose.
The best thing musing or any of us can do is report said accounts to the various services and blacklists, such as steemcleaners and others, and try to make it not worth their time and effort.
Even that is subjective. To some people if they make $1 a day they are happy, to others that is not worth their time.
I personally would love to see and hope that at some point musing will have the resources to "vet" more of the posts on musing. Eliminate the duplicates, the ones that serve no purpose, the "spam" on its platform. But even that will take much more resources than they probably want to devote to that.
After all musing is here to curate, not police