Yes, it's the case in practice: I've written a lot of @nogc code. Some parts of the standard library require the GC, but not all of it, and the parts that I usually use are fine (std.algorithm, std.range, ...).

Since allocators landed, it's been a lot easier, and I've written a library that does C++-style smart pointers for D:

https://github.com/atilaneves/automem