Sometimes it's obscenely complicated because the GNU devs like showing off with even the simplest of programs. My favorite example is GNU yes, a coreutil that's so ludicrously fast[0] that it can cause OOM states in mere seconds if you're not careful where you're redirecting output. Other HN users have compared the GNU version[1] with the BSD one[2], and I think it's a pretty good way to grok the difference in style between the two. In any case, both tools work perfectly fine for pretty much every use case.

[0] https://www.reddit.com/r/unix/comments/6gxduc/how_is_gnu_yes...

[1] https://github.com/coreutils/coreutils/blob/master/src/yes.c

[2] https://github.com/openbsd/src/blob/master/usr.bin/yes/yes.c