I've been writing graphing/charting code off and on for over two decades. My code has been used in high end audio software. Sometimes it's faster and easier to write the simple for loop that draws lines or splines on a canvas than to incorporate a "full-featured" charting library that has to support every kind of chart, plot, graph, network, 2D, 3D, etc. imaginable. A charting library that takes an array and makes lines is not that hard.

And yet I still had a dev get pissed off by my offer to help with a charting problem. "Yeah, but was it D3?"

I'm generally an advocate for buy-before-build in software, but I don't trust the kind of dev who won't even acknowledge that the easy part of a problem is easy (or that true experience isn't framework specific).

Indeed.

A couple of months ago, a junior developer mentioned he'd need a library for a bar chart, and asked for directions how to use it in an Xcode project. It turned out to be easier to draw the chart with a few rectangles, and the developer had one of those great a-ha moments.