Or you can take the extra minute to install them yourself with brew, this a complete non issue for anyone that understands the command line in the 21st century using MacOS. Also, I would never build anything against macos userland because it's almost never the target.
So what? Do you complain when apt, yum, dnf, pacman, ports, or any other package management system does a download? I bet you don't, so it's not really a usable argument. Secondly, yeah, not tainting my systems OS and system paths is a good thing and opt/ from the filesystem perspective is the absolute right place to put add on packages.
"The /opt/ directory is normally reserved for software and add-on packages that are not part of the default installation"