Depends on a specific codebase? I found exact opposite to be true - very hard to reuse code that was abstracted too soon, and abstracting copy&paste the right way is actually easier if you have it in multiple cases and can see how it was used.
How is it harder to copy/paste the helper method and modify as needed, vs tracking down and unifying multiple instances of the same code written slightly differently?
In Java, when I hit a bad abstraction, I hit the inline shortcut (command-alt-n) and then evaluate the resulting code with git diff. Other languages may be more manual, but, at worst, you just use ripgrep or similar to find all the relevant use sites and then manually expand the abstraction: this is only really a problem it the function is used hundreds of time: but, in that case, you can always duplicate the abstraction and rename.
My experience lines up with yours. Working in overly and poorly abstracted codebases dramatically hurts productivity. Poorly duplicated code increases the chance for missed patches, but poor duplication has, in my experience, been vastly easier to fix. One codebase comes to mind. Twisted Python. Multiple layers of inheritance, multiple mixins, and major overloading of methods. Just navigating the code was pain.
