So, the API of these auto clean up objects is high level. Now how high level is the implementation? If you wrote it yourself (you sound like you did), and the abstraction has few or no leak, I bet you had to write insanely low level code to achieve that.
I see only one reason to do that: you need performance so high that no garbage collected language could provide it; and the application is so complex that you have to write high level APIs. Not to mention that your application has to be basically bottleneck-free, or you would have used a garbage collected language, it's FFI, and C/Fortran for the tight loops.
To my eyes, that is a tiny niche. It may even be void. The "pure low level" and "pure high level" niches are both better filled by simpler languages. The "low and high level with bottlenecks" niche can be filled by a combo (a combo is simpler than C++, in my opinion).
Now, there is a huge niche best filled by C++: the use and maintenance of C++ programs. This is my current day job.
I see only one reason to do that: you need performance so high that no garbage collected language could provide it; and the application is so complex that you have to write high level APIs. Not to mention that your application has to be basically bottleneck-free, or you would have used a garbage collected language, it's FFI, and C/Fortran for the tight loops.
To my eyes, that is a tiny niche. It may even be void. The "pure low level" and "pure high level" niches are both better filled by simpler languages. The "low and high level with bottlenecks" niche can be filled by a combo (a combo is simpler than C++, in my opinion).
Now, there is a huge niche best filled by C++: the use and maintenance of C++ programs. This is my current day job.