Implicitness of destructors isn't a problem, it's an advantage - it makes code shorter. Freeing resources in an explicit way creates too much boilerplate and is bug-prone.

> With destructors, you need to know what type you have (not always easy to tell), then find its destructor, and all the destructors of its parent classes, to work out what's going to happen

Isn't it a code quality issue? It should be clear from class name/description what can happen in its destructor. And if it's not clear, it's not that relevant.

> Implicitness of destructors isn't a problem

It's absolutely a problem. Classically, you spend most of your time reading and debugging code, not writing it. When there's an issue pertaining to RAII, it is hidden away, potentially requiring looking at many subclasses etc.