The problem I have with the argument is that "improvement" needs to be something objective and measurable. "I'm throwing away old code because eww" isn't improvement. The two examples cited are very telling:
> Consider cases like introducing Kotlin to gradually level-up a Java shop.
But why? Introducing a second language to do pretty much the same thing is a giant leap in complexity and it's not obvious we'd get something real in return.
> What about a PostgreSQL operation rewriting SQL stored procedures in PL/Python?
Yet again, why? SQL is popular and very well understood, the alternative solution would be less portable and a rewrite would introduce unnecessary risk.
> Consider cases like introducing Kotlin to gradually level-up a Java shop.
But why? Introducing a second language to do pretty much the same thing is a giant leap in complexity and it's not obvious we'd get something real in return.
> What about a PostgreSQL operation rewriting SQL stored procedures in PL/Python?
Yet again, why? SQL is popular and very well understood, the alternative solution would be less portable and a rewrite would introduce unnecessary risk.