I've never had much use for Gnuplot. It can do lots of things, but in my experience, it's been easier to get what I want in other tools. Most of my plots are created in Python programs, Latex documents, or interactive web pages, where I use tools focused on that purpose and embed the code where it fits. For most of my one-off explorations there are better tools too.

If I'm using Matplotlib, I'm almost always plotting things calculated in Python, so all my data and variables are right there ready to go. I think the fine details are controllable in more programmatic ways than Gnuplot. I use other Python libraries when they're a better fit. Being Python and object oriented makes it easy to figure out how to do many things (e.g. autocomplete).

If I'm doing one-off throwaway plots, there are better and easier tools than Gnuplot: Desmos, GeoGebra.

If I'm making interactive demos, there are better tools than Gnuplot: Desmos, GeoGebra, JSXGraph, Jupyter.

If I'm plotting a function for a high-quality PDF document, TikZ gives me more control than Gnuplot, and makes it easy to make many plots with consistent (and changeable) style, though being a Latex-based tool it has limitations to go with its power. TikZ is great for diagrams too. Asymptote is more powerful than TikZ in some ways for this kind of thing, but often harder to use.

GNU plot syntax somehow feels less discoverable, less intuitive, one constantly needs to be looking at the docs while doing it, was my experience.

I can’t really disagree. It takes a while to come to grips with its concepts and language for settings. But basic plotting is concise and intuitive.

I was mainly commenting on its configurability. Gnuplot lets you (once you figure out how) control everything; for example, the exact shape of the arrowheads in a vector plot.

(The name is “gnuplot”; it’s not a GNU project.)