I was thinking the same thing. Modules are still not widely used, it is a reasonable guess that there are a lot of optimization opportunities left.

That is true, but on the other hand Modules were standardized more than 6 years ago.

Promises and claims have been made for longer than that on how Modules would have improved compilation times and made everyone's lives easier. In 2026, I still have to see any real evidence of that, especially when PCH + unity builds are much easier to use (except on damn Bazel, which supports neither) and deliver great results.

If after 6+ years of development Modules are still so far behind, it is fair to question if the problem is with the design/implementability of the feature itself.