I feel it is highly opinionated because they only officially support a fairly small amount of packages. They're not particularly more up-to-date than say openSuse Tumbleweed. A Debian netinstall is equally a barebones system I can install exactly what I am looking for, and don't need to fiddle with third party repo's like the AUR. As far as I know, almost every distro will let you do a barebones headless install, then build up your system yourself. Arch is certainly less opinionated than Ubuntu, but that's not a big accomplishment these days.

If I were to desire a highly specific environment where I wanted to exactly manage each program's dependency chain myself, Gentoo seems like a much better tool for the job. For example, Arch officially requires systemD, Gentoo does not. As far as I know Gentoo makes no assumptions on how your system is setup, from preboot to Wayland session.

I could just be out of date, as I use NixOS as my workstation and server OS, using Debian for some older servers I haven't migrated yet. I get the impression from Arch, the few times I have used it, is that its niche is appealing to a particular kind of user, rather than being a good solution to a particular kind of problem. That's not bad, its huge reason why its popular. Other distros do the same thing as Arch, sometimes better sometimes worse, but Arch is selling an aesthetic, rather than a tool.