Joking apart, I reckon that Yuncheng IELTS and the like, as employers in China, do serve a useful purpose for FT's sixty and over, most of whom are greybeards, including old goats like Paul and Ian.
What's more, such recruiters also serve the same purpose for FT's lacking the mandatory educational requirement of holding at least a bachelor's degree from a Western university.
You see, such recruiters are vehicles for the aforementioned kinds of foreigners to teach in China, though the latter will necessarily be doing so illegally on F visas. Even so, they needn't concern themselves about the illegality of their actions because the local authorities won't lift a finger against them in third tier cities where the local government and their Chinese employers are in cahoots.
Yuncheng IELTS and the like are definitely of use to some of our fellow foreigners by providing them with gainful employment in a land where it's not uncommon for there to be no rule of law. Maybe when you reach sixty and wish to continue teaching in China, your only way will be to work for such a recruiter! So, my view is that we shouldn't slag such recruiters off!