It's perfectly reasonable for critics of powered flight to point out that steam engines will never be truly useful for the job if that's the only kind of attempts at powered flight that anyone's shown, and they've been claiming that steam engines WILL actually get good enough, just you wait and see!
Of course we can't predict rapid introductions of heretofore-unknown technology, but that doesn't mean that every scam artist and huckster should get a free pass because there MIGHT be a shiny new technology just about to be discovered that will retroactively make their wild claims sound prescient.
