It's not as simple as use a better language. Often, various organizational constraints Are preventing this. I tried building a new micro-service in Kotlin, right after spring released official support, and there was an incredible reluctance for some team members to learn it. The service was still spring boot with most of the standard patterns but just different enough to make some uncomfortable. Inertia at big companies makes change hard

Edit: The kotlin service was one internal service that I experimented with. Our other 17 production services were standard java spring.