Yes, the steam powered airplane is a dead-end branch in the development of the airplane. Unlike most of the dead-end branches, it actually worked, in a limited technical sense.
Most research and technological development fail, and most of those which succeed in a technical sense end up being worse in a practical sense than other alternatives.
There are a lot of gadgets where "the creators and innovators are told they are wasting their time, suckers, look how many failures came before you" -- and the detractors were right.
The screw-propelled vehicle, after over a century of development, has slightly more success than the steam airplane because there is a niche use as amphirols. But for nearly every case it was designed for, caterpillar tracks, half-tracks, or even tires are better.
No matter how much R&D you put into it, it seems impossible that a roller ship like the Ernest Bazin will have commercial success. Ditto the gimbaled cabin design of the SS Bessemer, meant to stave off seasickness in the passengers.
Various gadgets lie on the border where they seem tantalizingly commercially realizable, like kites on container ships. That's where kooks and hucksters thrive.
