It's not gated by median skill.

Rather, it's the level of effort required to standardize, carry over, or reproduce a particular feature in the disparate environments we use.

Say Windows maintained that filesystem transactional feature. It'd be exposed in their C++ (?) API. What if you wanted to write your program in Python? What if you wanted to port it to Mac? Linux?

It just takes time for such platform features to percolate to the various environments that could use them.

I do not see how it follows. A smart developer will choose a database, not a file system, if data integrity is important. So it can be simply the case that the transactional API with a lot of its limitations were simply not flexible enough for people to bother.

Nonsense. It's "gated" by common APIs available in programming languages.

If this feature is Windows-only then barely anyone would take the requisite time and effort to use it properly.

Have a POSIX-like API that is supported at least on Win / Mac / Linux and you'll see people adopting it. Before that, no chance. It's not justified.

And you just described why Rust is such a great choice for a open source project over C/C++.