It's just a very loaded opinion, while you pretend it's a universal fact. I have never heard, nor experienced, any seasoned C++ developer claiming that smart pointers is a substitute for garbage collection.
Yes, smart pointers are nice, they alleviate you from a whole lot of manual memory management - but the programming model is still vastly different from what you would do in a traditional GC'ed language(such as Java or C#)
A lot of C++ big names have said that smart pointers are better than garbage collection for handling resources. And they are, because GC only handles memory.
Having memory leaks in modern C++ is a sign of not keeping up with the established idioms. Saying that experienced C++ programmers are worried about memory leaks is bizarre.
Yes, smart pointers are nice, they alleviate you from a whole lot of manual memory management - but the programming model is still vastly different from what you would do in a traditional GC'ed language(such as Java or C#)