Is this a cheap shot? Not really. Is it fait to pick and choose one "mistake" to shame all bankers? Well, yes. I tell you why. The "mistake" was not a rare instance. Their wins and losses are about the same, give or take that they were maybe 65% right all the time. But the instance they were wrong will cost you big time.
That's because investment bankers are in the business of SELLING. They need you to move your funds. To sway you to move to something, they will have to dissuade you from the prevailing choices. Even though they may not know much of other options, in the business of selling they will tell you don't go there vehemently.
They do not have your best interest at heart, but their quotas and bottom line for the year. You are not going to hear "I don't know much about other options you mentioned, let me check it out".