Ime you kind of do, at least did. I learned rust twice I think. First time it had a lot of time hype so I sat down and learned it. Then kind of like this rant never used it so it forgot it.

Then it came up at work and the language changed enough that I had to learn it again. Features were added, the "community approved" libraries changed, tools changed, coding conventions changed.

I never had that feeling with any other language I've used in similar ways. Javascript, ruby, python go I always felt like I could learn, stop using and come back to use pretty easily.

I have difficulty picking Rust again for semi-different reasons than yours: it simply has a huge surface, not only the core language but also the libraries; the amount of those you really must know to be able to call yourself a commercial Rust programmer seems to grow with time. (You mentioned this last point, hence the "semi-different reasons" expression.)

I know Rust quite fine as a language but put me in a commercial project and I'll definitely need a few weeks to learn what should be used for i.e. error handling, logging, OpenTelemetry, and such.

C++ has changed a lot.