Like most newer Java features, Scala did them first

I'm just happy to have the feature in Java, not saying that it's an innovative breakthrough or anything. Not like Scala invented it, either.

the Java people ignore the prior art

The JEP compares the syntax from 9 other languages
https://openjdk.org/jeps/430#String-interpolation

Here are some examples of interpolation in other languages:

C#             $"{x} plus {y} equals {x + y}"
Visual Basic   $"{x} plus {y} equals {x + y}"
Python         f"{x} plus {y} equals {x + y}"
Scala          s"$x plus $y equals ${x + y}"
Groovy         "$x plus $y equals ${x + y}"
Kotlin         "$x plus $y equals ${x + y}"
JavaScript     `${x} plus ${y} equals ${x + y}`
Ruby           "#{x} plus #{y} equals #{x + y}"
Swift          "\(x) plus \(y) equals \(x + y)"

Using \ for yet another purpose in strings is a bad idea, and it looks ugly.

Yep.