It might be that they use simple in relative terms.
Linux could be considered simple given the problem it's trying to solve and yaml complex.
Linux could be considered simple given the problem it's trying to solve and yaml complex.
For example they might think that in a mixed-paradigmatic language the "pure functional approach" is more simple even if it introduces more indirection and requires a deep understanding of various more advanced language constructs(*).
Or that the simplest explanation of monad is the one based on PL-theory instead of an explanation based on terms people without an scientific-PL background are more familiar with.
Or people which think that writing down things in predicate logic is just way simpler then writing them down in English (well, I guess thats somewhat me).
None of the "I find this is simpler" points I mentioned are bad, but not realizing/accepting that what is simpler for you isn't simpler for others is the problem.