What are some good resources on writing idiomatic Kotlin? I always feel like my code, the bigger it gets starts to look more like Java/C.

Did you read the official Idioms page? It's a good start 🙂

Effective Kotlin maybe?

Also to some extent just using IntelliJ, the static code analysis is quite good in highlighting some idiomatic Kotlin functions you can replace existing code with. Especially valuable every new Kotlin version when new APIs are released.

if you don't mind diving a bit into functional-style idioms, https://arrow-kt.io/learn/design/ has several tutorials and guides

Thanks everyone! Very helpful

What do you mean that it starts looking like Java/C? They are wildly different