My opinion is somewhere in between. Descriptive error messages are always good to have, there is no reason to not implement them. On the other hand, this feature is of a very low importance to me. I don’t remember the last time I got NPE in Kotlin and even if that happens, it is usually very clear without a good message as there are very few places in the code where NPE may happen.
Also, !! is for pretty rare cases when we are sure a variable is not null, because there is some nullability logic that can’t be easily represented statically. We should avoid it if possible.