The points you bring up don't seem to support your argument. It took a decade from when people first attempted to haul freight with a steam locomotive until the first commercially successful railway was built. If you start counting from when the steam engine was first invented then it would be more than a century. You're correct that a lot of that success depended on improvements in manufacturing capability but I don't think it's so obvious that there was a huge market for steam locomotives right from the start, early steam engines were notoriously fickle, required constant attention and a trained engineer, needed specialized tooling and materials to repair when they inevitably broke, and they were incredibly inefficient and fuel hungry at first. That's why they started out so linked to coal mines, the mine produced enough cheap fuel for the engine and already had a lot of the metalworking tools and capable engineers needed to maintain it.

I'm not sure why you don't think space is commercially viable right now, companies and governments are paying a lot of money to have things delivered to orbit. SpaceX is making money with every launch otherwise they would have gone bust years ago. If you mean there's no market for human spaceflight, well there wasn't a market for passenger railroad travel for a long time either. You need to build the railways before people can make practical use of them. Back when most railways only extended for 1 or 2 km it was pretty hard to imagine getting paying passengers. You have to build something that connects to places people want to go before they'll pay to ride it.

With spaceflight we're currently in the shorthaul stage, all the profit is in delivering cargo to LEO. The cost is coming down and people are finding more uses for cheap satellites. The rockets already have their use case, they move people and cargo the same as a railroad, it's what we do with that capability that we need to get creative with and as we continue to build out capability and lower cost there will be more and more uses for space. The main reason I compare it to railroads is that it is a type of infrastructure that makes new things possible and there's always a profit to be made in a frontier as long as you're daring enough to take it.

Yeah; I would compare railroads/rockets to microcomputers/VR. The latter is definitely impressive, and unique, and evocative for futurists, and has some niche use-cases, but doesn't have a clear "killer app". While the former had people - real businesses - chomping at the bit even before it became economical.