If you've seen my posts you know I'm generally not a fan of cash cows. They tend to be overrated fighters with rabid fanbases. Sometimes the skills are real, sometimes it's mostly smoke and mirrors. Who do you see as the LEAST skilled (most over hyped) cash cow of the past few years?
Garcia. He's fairly offensively inept despite his physical gifts. He's got a great left hook, but doesn't know how to properly use the jab and he doesn't know how to put shots together. Worst of all, he's got low boxing IQ.
Ryan. Great left hook but too predictable. Canelo might be overrated to some degree and he has certainly received biased judging. Yet he is one of the most well rounded offensive fighters i have ever seen - great left hook to head and body, great right hand, powerful uppercuts with both hands ( a rare skill), great body puncher, excellent counter puncher, and probably the best head movement in the game today. I don't think anyone can make a case for him being the least skilled star. Joshua is one of the better combination punchers at heavyweight. His chin let him down sometimes.
It's a difficult question... Partly because you also ask it as if least skilled necessarily means most overhyped - and I don't think that's necessarily true. The least skilled on your list is realistically Ryan... But the most overhyped is Tank - it's just that he so rarely put the skills to the test in order to prove whether he measured up to the hype - the skills are there, clarity around the levels he can be successful with them is not.
Ryan, Ryan is a cash cow for more of his out the ring personality as than his in the ring prowess. He's not devoid of talent, he's a bit of a physical specimen, but he's not a very disciplined, highly skilled guy at all.