I think this is unfair - Arch is also meme'd by linux enthusiasts and 4chan.
Additionally, Gentoo is the largest distro with the source-based package manager USP. I suppose you could take issue with that approach for reasons like the systemd maintainer does where he claims it wastes CPU-cycles and time. Personally I disagree with that assessment since reproducible builds are a vital part of FOSS.
Fun fact is that Gentoo is the most normie distro. ChromeOS is based on Gentoo and all have coreboot. I'm not disparaging it as much as seeing it as a similar learning tool.
This is partially true but I believe that the only component ChromeOS uses from Gentoo is the portage package manager during some of its bootstrapping protocols.
I was never a gentoo user (I installed once, like I did for basically any distro back then), but I wouldn't knock the sort of "apparently-unproductive tinkering" that Gentoo epitomizes. Like building the umpteenth blog engine, or yet another Todo manager in $language_du_jour, that's how we learn.
I use gentoo on my desktop and debian on an old refurb thinkpad I got for £100. Both of them are amongst the last of the large independent linux distros and I think both approaches are valid.
Never had a bad experience with Arch but the way they use the AUR as a crutch is a bit off-putting. It's a little bit like a giant gentoo overlay but pushes all the complexity onto the user.