maybe you have something like old kotlin-stdlib (which overrides jdk8 transitive dependecy)

kotlin-stdlib-jdk8 itself is a very small artifact which provides a few classes for Java 8 support, but it itself has kotlin-stdlib in dependencies

also, check that you don’t have

kotlin-stdlib-jre8

this is old name of the same artifact which existed before Kotlin 1.2, so it may also bring old stdlib to classpath and I not sure how maven dependency resolution will work in this case