while cool, it's pretty telling that similarly high-level languages like C#, Kotlin, Scala, Python, Swift and Javascript have had this widely-used quality of life for years while Java doesn't

And by telling I think you mean that over time Java has very thoughtfully evolved in a way that respects backwards compatibility, or that once a feature is in the language it'll very likely stay there for the next 25 years. Yes, innovation is very important (and happening faster than ever now with the 6-month release cadence), but a majority of the work isn't in deciding what goes in, it's deciding what stays out and if something does go in how does it satisfy both audiences of "move slow don't break" and "move faster we want features".

A good video on this process: https://www.youtube.com/watch?v=2y5Pv4yN0b0

Thanks. Looks very interesting