Ummm.. this is pretty basic stuff. If you don’t know this, you probably shouldn’t be claiming to be a c++ developer.
A bit of a shame because C++ 14 and onward really closed all those gaps that devs used to rely on boost to get extended use out of, but I guess that's how a culture develops where there is no central package management repo.
As you yourself have implied, you have to _start_ somewhere.
That's why the yearly salary of a senior C++ dev can vary a lot, usually from 1x to 10x.