One of the improvements that made making Kotlin DSL the default for new Gradle builds possible was a simpler way to assign values with lazy properties.

Gradle Blog

Gradle 8.2 introduces simpler property assignment syntax in Kotlin DSL, allowing the use of the = operator directly on lazy Property types instead of the verbose .set() method. This was made possible through a Kotlin compiler plugin developed in collaboration with JetBrains, marking the first externally contributed Kotlin language feature. The change reduces verbosity, standardizes property access, and eases migration from Groovy DSL to Kotlin DSL. The feature is enabled by default in Gradle 8.2 but remains incubating until Gradle 8.3.

Simpler Kotlin DSL Property Assignment