I think JetBrains has fully bought into Gradle. I think Maven support has been less and less over time, which shouldn't be a surprise. Gradle supports native Kotlin build scripts (i.e. build.gradle.kts), as well as putting a lot of work into ensuring their tools fit well within the Gradle ecosystem (exhibit A: https://github.com/JetBrains/intellij-platform-plugin-template). I think it only natural for the creator/owner/maintainer of Kotlin to go full in on the build system that supports the language!
controversial take: who still uses maven? who would prefer xml files over build scripts? (ok... fine, big timers like RedHat definitely do, or at least, have never taken/don't want to take the time to upgrade lol)
I prefer Sealed Secrets over sops since it has the namespace scoping element and can also be stored in repo (once encrypted). I also generally prefer having a controller deployed rather than forcing devs to learn kustomize (which we don't widely use yet) so I guess less of a support burden for me.