Comment by MrScruff

I think there's some truth to this. The assumption that there will be low hanging fruit in the profiler when you eventually start worrying about performance isn't always true.

Also, the more you worry about writing performant code, the easier it will be for you to write it that way in the first place without making sacrifices in code readability or maintainability. It's a myth that high performance code is always more complex and error prone. If performance is always something put off as something to address later, you can end up with as you describe 'a giant mass of moderately slow code'.

What I do agree with is that picking the correct data structures has more of an impact that algorithm noodling, though that has it's place.