Lifetimes are the input to the borrow checker, so it doesn't make much sense to say you have never been bothered by the borrow checker but you are bothered by lifetimes.
I believe your parent is implying that if you skip using a lifetime and do something else instead to make it easier, that may be less performant.
Cloning values, collecting iterators into Vecs and then continue the transformation rather than keeping it lazy all the way through. Skipping structs/enums with references.