2. It is worth mentioning that by the standards of your comment, the time between conceiving of a classical computer (Babbage) and a scalable electronic computer (ENIAC and family) was about a century.
3. While ultimately there might be a "quantum winter" in the next few years because we (I work in the field) overpromised, this would not be the first time a tech that ultimately works gets disregarded for a decade or two because of mismanaging expectations (e.g. Liquid Crystal displays or neural networks, which were both developed for many decades before being commercially viable).
EDIT: And yes, there are some startups with misleadingly general pitches.
