Im currently the COO of The Freelance Movement and DoMoreGiveMore Pro Group.
These companies do 8-figure and 7-figure respectively while the CEO can still take a vacation without worrying about their business.
I know when people talk about systems they always talk in revenue, sales etc. While nothing is wrong with that and that I have much respect for the hustle culture.
My measure of success when working on the back-of-the-house of the business is the amount of reduced hours the CEO gets, the additional time-off the team gets and while the business keeps on running.