So there was an era, as the OP says, where your arguments were popular and believed and it was understood that things would move in this direction.

And yet it didn't, it reversed. I think the fact that "plain text for all source files" actually won in the actual ecosystem wasn't just because too many developers had the wrong idea/short-sightedness -- because in fact most influential people wanted and believed in what you say. It's because there are real factors that make the level of investment required for the other paths unsustainable, at least compared to the text source path.

it's definitely related to the "victory" of unix and unix-style OSs. Which is often understood as the victory of a philosophy of doing it cheaper, easier, simpler, faster, "good enough".

It's also got to do with how often languages and platforms change -- both change within a language/platform and languages/platforms rising and falling. Sometimes I wish this was less quick, I'm definitely a guy who wants to develop real expertise with a system by using it over a long time, and think you can work so much more effectively and productively when you have done such. But the actual speed of change of platforms and languages we see depends on reduced cost of tooling.

For me, that's what "short-sighted inability" means. The business ecosystem we have does not have the attention span for this kind of project. What we need is individuals grouping together against the gradient of incentives (which is hard indeed).