Something like the original computers, Eniac etc, were actually generally useful. It was useful to very large enterprises that previously relied on an army of human "computers" but it was useful for them so it stimulated refinements like the PDP-8.

I think if you went back in time you could pay some power loom engineers to build you a pretty decent 4-8 bit microcontroller operating at 1-5 Hz (comparable to power looms at the time) and computer-controlled textiles would have paid for the computer revolution 75-100 years ahead of time.

Would it? You have to remember that the further you go back in time, the cheaper labor is relative to machinery. In the 19th century, you could pay a person for a multitude of customizations and so the market for custom cloth might not have been what you imagined.