Nothing much has changed beyond C and the FTP-zip-tar-configure-make landscape since, what, 1980? The distro package systems have improved things a little.
This will have a bigger impact on the language than a lot of the individual library incorporation that's been going on.
Prior to that, it was FTP-uncompress-untar-edit config.h-make.
You'd be expected to spend 10-30 minutes scanning a long config.h file or similar and adjusting as per your local unix variant. Often a BSD or SVR4 like system (rarely both) would work mostly out of the box. AIX, Ultrix, or HP-UX were more troublesome from what I can remember, SunOS or Solaris (never both ;-)) would mostly work out of the box as that was commonly the dev platform.
Wouldn't you rather have one # decl that does all the legwork of installing a dependency for you, plus all the things it depends on? All these cool kids' languages have that stuff builtin now. Or at least builtin one level away, ie gem, "go get", gradle, etc and ilk. It's so convenient. I dread that part of c*.
It will encourage some horrendous levels of indirection in dependencies that cpp currently doesn't suffer from. I've been doing this for 7/8 yers and I don't feel inconvenienced. Indeed I think it represents a decent quality control step