Gentoo Linux might be the best desktop Linux distro for advanced Linux users

Disagree.

I'd say it's more akin to learning vim, where there's a fairly steep learning curve at the outset, with huge rewards down the line.

Yes, initial install can take a while. Yes, system updates take longer when built than from binaries - but modern hardware makes that a fairly trivial difference. Most people who have a problem with Gentoo either only used it decades ago when build time were a lot longer, or because they heard it takes long, which is way more common than the former.

Huge upside.

You need two sets of the "same" hardware, though. Then you get a build server with -march native

I used Gentoo since about 2012 up until 2022 then switched to Debian mainly because lot less things used to break during updates and my old CPU ( i7 4790k ) became a bit dated to compile every new version of Golang, Rust and Chromium - just hours and hours of brutal grind. Since flatpak can provide up to date versions of a lot of desktop software on Debian there is very little point switching back. Maybe one day if I get my hands on some ridiculously powerful CPU like 7800 or 9800X3D then might try it again.

With malware reportedly uploaded by random people to AUR, I will stick to Debian.

A good thing about proprietary OS is that, they are responsible if their repos are infected.

Are packages carefully reviewed by gentoo?

Twenty years ago, Gentoo taught me Linux.

A friend and I wanted to play around with Linux, so we installed Mandrake[1] Linux on a school PC. We didn't know what we were doing, and the GUI (I think it was KDE3?) abstracted too much. It was also very unstable.

I don't remember how I got to know about Gentoo, but I then proceeded to install and reinstall Gentoo on my home PC (Athlon 64) about 20 times, and this was when you had to start from stage1, so you had to do a full bootstrap, kernel, and system compile; no binaries and no shortcuts. The scrolling gcc output on my screen was the coolest thing ever.

The Gentoo handbook was amazing. It taught you exactly how Linux works and how to install every component of the system.

After a while, I began contributing to the distro and even became a developer for a few months but had to quit due to real life.

I don't follow Gentoo today, but if it's still valuable as a tool to learn Linux, I can highly recommend it.

[1]: https://en.wikipedia.org/wiki/Mandriva_Linux