I agree with your point, but for completeness:

> How is not having to mark your unsafe code as unsafe a good thing?

The problem with unsafe code in Rust is that IIRC nobody actually figured out yet the "rules" of unsafe i.e. which invariants you can stretch and which can cause UB. My (not super up to date) understanding is that this is an active area of research and progress is being made and also that in practice there are many well understood usages.

In short unsafe rust is somewhat worse than C++ as the boundaries of UB are less well understood/defined