depends where you come from. If you come from Python, Java, you'll find that there's a lack of support for networking, etc. and that it is not vast at all. After all we lack a W3CEndpointReferenceBuilder (
https://docs.oracle.com/javase/10/docs/api/javax/xml/ws/wsad...).... not sure how it's possible to be productive without that.
If you come from C you'll think that there are allocations everywhere and judge it unfit for purpose (even if in my experience, C libraries and software tend to allocate much more than C++, and use worse datastructures like linked lists, etc. just because it's easier to code in C).
Finally the C++ committee and standard library implementers refuses to break ABI / API, which means that :
* the C++ standard is not able to follow the state-of-the-art for e.g. hash maps, as the fastest hash maps (if you only care about speed of insertion / retrieval, which is let's be honest 99.5% of the use cases out there) because unordered_map has strict requirements that these newer hash maps do not satisfy.
* things like regex stay broken