This strikes me as a compiler and IDE feature, rather than a reason to have a separate programming language. What does having a separate language give us as op

This strikes me as a compiler and IDE feature, rather than a reason to have a separate programming language. What does having a separate language give us as opposed to taking say, Kotlin, and having a compiler that stores the AST/whatever in a database and does all the interesting goodies? Or is that the end goal, but we're using a basic language to test it out and work out all the quirks before writing a compiler for existing languages?