Kotlin does not lock you in and has not locked you in to IntelliJ. About a year ago, I coded up a Kotlin service using VS Code. See https://glennengstrand.info/software/coding/csharp/kotlin for my description of that including how nice the developer experience was under VS Code. The plugin I used was https://github.com/mathiasfrohlich/vscode-kotlin which works like a charm.