Until I moved to FreeBSD in the mid 2000s I ran Gentoo primarily. Even though it had a bit more hand holding than LFS, it still taught me a lot and getting to choose implementations allowed consideration of design choices (cron, mail, syslog, etc.).
I’ve tried to return a few times but it’s a bit different now and I’m happy enough with FreeBSD that I don’t have much place for it. I do wish more embedded distros would have started with Gentoo (specifically ARM SBCs).
I think one of the advantages of Gentoo or LFS is you get an “introduction” to a bunch of the various parts, so that when you need to change something in the future you know where to start looking.
Somehow LFS didn't help me understand the various subsystems... all I remember is long sed patches and compilation logs
It did teach me how subtle a running stable OS is underneath though, as, after my first standalone boot, I could enjoy a partially working TCP stack: elinks could browser, curl couldn't, irssi sometimes, all of this with random terminal display codes being inserted.
From there I moved to Gentoo, and then eventually to Ubuntu and other batteries-included distros. But the knowledge I gained from LFS is still a foundational part of my skillset, even though my roles have been more dev-focused than ops/infra.