Well, you really have answered your own question. You must find the sweet-spot.

Let's start with one end of the continuum: no 'helper' routines. We all should agreee that that's just not a good idea. To a certain extent all functions fit this definition. Sometimes they're tiny, and sometimes they're complex, but any time you call another piece of code, you're reusing it, and the programmer calling it might not understand how it works. Sometimes that's OK. I use stuff from CPAN that I don't understand, but to a certain extent, that's the point. I don't have to understand, I don't need to understand, I don't even *want* to understand.

At the other end we have the old cargo cult phenomenon. It's real easy to be bad-lazy and reuse code in the wrong way, or in a very inefficient way. I think this is where experience is important. A senior programmer can look over a juniors work and make sure that they're not drifting too far into the weeds and at the same time, they understand the pertinent parts of the project.

I work alone, and this lack of peer review (formal and informal both) is without a doubt the single largest drag on my effectiveness and productivity. So, good luck, and make sure to have seniors and juniors working together.