FWIW the cool thing about gentoo was the "use-flags", to enable/disable compile-time features in various packages. Build some apps with GTK or with just the command-line version, with libao or pulse-audio, etc. Nowadays some distro packages have "optional dependencies" and variants like foobar-cli and foobar-gui, but not nearly as comprehensive as Gentoo of course. Learning about some minor custom CFLAGS was just part of the fun (and yeah some "funroll-loops" site was making fun of "gentoo ricers" way back then already).
I used Gentoo a lot, jeez, between 20 and 15 years ago, and the install guide guiding me through partitioning disks, formatting disks, unpacking tarballs, editing config files, and running grub-install etc, was so incredibly valuable to me that I have trouble expressing it.
I still use Gentoo for that reason, and I wish some of those principles around handling of optional dependencies were more popular in other Linux distros and package ecosystems.
There's lots of software applications out there whose official Docker images or pip wheels or whatever bundle everything under the sun to account for all the optional integrations the application has, and it's difficult to figure out which packages can be easily removed if we're not using the feature and which ones are load-bearing.
I started with Debian on CDs, but used Gentoo for years after that. Eventually I admitted that just Ubuntu suited my needs and used up less time keeping it up to date. I do sometimes still pull in a package that brings a million dependencies for stuff I don't want and miss USE flags, though.
I'd agree that the manual Gentoo install process, and those tinkering years in general, gave me experience and familiarity that's come in handy plenty of times when dealing with other distros, troubleshooting, working on servers, and so on.
Someone has set up an archive of that site; I visit it once in a while for a few nostalgiac chuckles
https://www.shlomifish.org/humour/by-others/funroll-loops/Ge...
Nixpkgs exposes a lot of options like that. You can override both options and dependencies and supply your own cflags if you really want.