True, although that has a way of becoming important after awhile. That’s why I prefer to focus on complexity and clarity as it’s much harder to make convoluted code when it becomes important.
It’s nit picking, but I think a more correct statement would be “lots of small performance mistakes add up over time”. It’s very rare that I see a project needing a new language for performance reasons, but I see projects that need refactoring for performance all the time.