With the exception of CMake evolution (now days a defacto standard), package managers (as Conan or vcpkg) or the support for new C++ standards in major compilers (clang, gcc, Visual) ;)
It needs more guidance for making simple, typical projects easy to set up, at the very least more stuff that works like ExternalProject_Add (a big powerful command with all its options clearly documented on one page).
1) declare your dependencies in a vcpkg.json file (similar to npm's package.json). Example:
{ ... "dependencies": [ "openssl" ] }
2) Add it to your CMakeLists.txt file. Example:
find_package(OpenSSL REQUIRED)
target_link_libraries(main PRIVATE OpenSSL::SSL OpenSSL::Crypto)