It seems like there a bunch of articles there but they're more like notes on how to use a tool specifically with Arch, rather than a guide for everyone.

Compare this page http://www.tldp.org/HOWTO/Quota.html to this page https://wiki.archlinux.org/index.php/Disk_quota . TLDP organized HOWTOs like mini-books; tables of content, multiple authors, versioned releases, and of course, you could download them all and search through them by category. And they didn't assume things like the distribution setting up a bunch of the tools and system for you, so you learned how the tools actually worked.

Sure, it's a different format. But you can always dig into man pages or other documentation to learn the details. Arch wiki is great for practical solutions - for example https://wiki.archlinux.org/index.php/HiDPI is the place to go to for hidpi display configuration. TLDP has not been seriously updated since hidpi even came out. Similar to https://wiki.archlinux.org/index.php/Power_management - there's no recent TLDP equivalent.

I appreciate TLDP for what it is and the details they go to. But Arch wiki can easily be read as a FAQ for all modern systems. And it will usually send you to other places for details (sometimes TLDP as well)