[aninhumer]

I think saying something it's simple because it's based on simple rules can be slightly misleading. This is why I like to distinguish the ideas of "complication" and "complexity".

To me "complicated" means that the rules of a system require a lot of information to describe, i.e. it has a lot of special cases and caveats to learn. Whereas "complex" is more about the variety of emergent patterns in a system which are necessary to understand it and interact with it effectively.

As an example, rules of Go are very simple, but we probably wouldn't call it a simple game. In contrast, the rules of Chess are rather more involved, with quite a few special cases. Both games can be called "complex", but I'd also say that Chess is more complicated.

So using these terms, it sounds like you're saying Scala is less complicated than Kotlin, whereas the parent is perhaps saying that Kotlin is less complex?