is it uncommon to use primitive array types (IntArray, BooleanArray etc) in Kotlin?

As it was said, it's depends on your usecase, but in general because arrays are pretty limited in many aspects it's much more common to use List instead, and use arrays as performance optimization in some cases and usually do not expose it in public API

Thank you

Integer[] is boxed, non-primitive array, so ArrayList<Integer> would be very close by performance, you just pay price of additional object But int[] (or Kotlin IntArray) is better in terms of memory and allocation (get/set complexity is the same as List<Int>)

I'm just trying to figure out what the point of Array<> is

Array<T> is just a platform primitive (part of memory with references to other objects), for example point of it to implement other, higher level collections, ArrayList (and many other data structures) are based on generic array

I see, thanks for the explanation