Experience over theory. Your theory of why it is bad lacks mathematical backing, and your lack of experimentation of it shows your disregard for empirical conclusion. Tell people how wrong someone else is until what they are doing becomes the norm, then be wrong yourself, or analyze it with an eye for why it might work versus why it would and make a case based off of some sort of actual data of ANY kind.
Furthermore I never said it is OP, but it could work, could in fact be gamebreaking in the right environment. Whether that environment exists now or will exist in the games you play who knows, but if you don't know when it is powerful you may never build it when that opportunity arises.
Some time back I said Zzrots portal was good, people told me I was wrong, now it is considered good. /shrug Believe what you will, but don't hold that belief so hard that you tell people they are wrong, they could just be ahead of the curve.
You could be right, I could be wrong, or maybe it is better than you think but limited in application. As I have said before, people tend to expect Yorick to be tanky, but sometimes it is better for him to just be a hobbling hammer of doom that obliterates squishies all day.
Lastly, mechanical prowess is very much connected to itemization, as if you don't know exactly how and when to utilize a champion to their fullest you often cannot get the best out of their itemization. Thus you may end up relying on itemization that doesn't require good mechanical skills. It can be tedious to orb walk on Yorick, but doing so well makes the build the creator of this thread suggests very powerful indeed.