I'd certainly agree that malloc is the Achilles heel of any real world C. Overall though C++ was not a particularly good solution to memory efficiency since having OO available made the situation look like a fast sprint to the cake shop.

Heavy smalltalk-style OOP in C++ has kind of died out, especially with data structures. So with any templated data structure you’re reducing indirection from vtables and you have the opportunity to allocate however you want, often in continuous slabs to ease memory transfer and caching.