The fact that you need to invoke lsblk/blkid/mount first to be sure what you're about to erase forever, then possibly sync and unmount, and only then format. Keeping the same target device at every step is completely on user and the price of a typo is huge.
I love (and usually prefer) the Unix way, but it's as dangerous as it's powerful and the amount of the required prior knowledge is incomparable.
Of course there's GUI solutions for GNU+Linux, but I was specifically answering to your "what's wrong with mkfs" comment.
Moreover, the GP mentions "as a kid" which is probably at least 10 years ago, when the choice of GUI tools and their availability in various distros and their repos was much more limited.
Those are the low level tools. there are things like parted that bundle them together if you want something more guided. GUI versions are available too, and since many installers ship with GUIs these days you don't even have to touch the terminal anymore.
Unless you install arch, but then learning the plumbing is part of the experience.
Discoverability. The Windows approach is kid friendly because you can discover it by right clicking on a drive in Explorer, ignoring every option you don't understand, and pressing start.
Knowing that "mkfs" is a thing or that "/dev/sdc1" is a thing pushes the minimum knowledge requirements orders of magnitude higher.
