I've heard "monomorphisation" to refer to something a compiler does, but not something a programmer does. I think this is just "repetition"!

The need for something to solve the problems inheritance solves has been known in Rust for a long time. Mostly it's been motivated by the need to implement the HTML DOM, which is fundamentally an inheritance hierarchy, in Servo. There's a longstanding RFC about it:

https://github.com/rust-lang/rfcs/issues/349

Inheritance is one possible solution. There are others.