Boost libraries used to be cutting edge, to such an extent that they were adopted into the C++ Standard. And now the progress is in reverse. The Standard introduces a new component, and the Boost library follows (Boost.Charconv for example).
Does a component need to be new to be valuable? You are correct that Charconv does not implement a new, or novel interface. In fact to the user it's really just 2 functions. The value proposition is that it's quite good at what it does and is available today. The library will benefit users of other libraries like Boost.MySQL and Boost.JSON at low cost to those maintainers: https://github.com/boostorg/json/pull/993. One of the big pushes for C++26 is BLAS. I'll bet if you look hard enough you can find a box of FORTRAN punch cards with a reference implementation on it. Because it's not new is not valuable? There is still quite a bit of research going on in the problem space: https://arxiv.org/abs/2210.10173. The users of boost are looking to solve whatever problem they are paid/want to solve. Offering novel components is cool and all, but offering well-engineered solutions to pervasive and mundane problems (like parsing numbers or matrix algebra) is valuable in it's own right. Matt