A business plan is nothing more than an idea wrapped up in some estimates and guesses. Sure, you can do "market research," but those are nothing more than guesses and they usually turn out to be wrong. So in a sense, when you criticize money being thrown at an idea, you are criticizing the notion of business plans. My point was that business plans are a negative signal because all it indicates is that you have an idea and that you haven't built anything to test your idea.
It is not a point of whether or not you can put your idea on paper. It's a point of wasting your time over-analyzing things you cannot know - and then putting all that useless analysis on a multi-page business plan or a 15 slide presentation, etc.
No, it is not the case that Silicon Valley just throws money at ideas (alone), and you're arguing against a straw man if you think I ever made that point. In fact, the process of building a prototype and validating your product by testing it in the real world is the quickest way to get huge multi-million dollar valuations in Silicon Valley. The exception would be having a very strong team with experienced founders.