Pictures are worth a thousand words but if you don't know which words you want to communicate your picture is worthless. Something many artists eventually learn, what is it you actually want to say?

Diagramming is interesting because it relies heavily on writing, half of a diagram are words. You can slap on as many triangles, circles, and lines as you want to communicate your idea but if you do not utilize the right words it's a worthless diagram.

An HTTP request-response diagram is a great example of this. You can overcomplicate it with both symbols and text, you can also miss crucial points and give people the wrong idea entirely.

So let it encourage you to pick up drawing/diagramming tools, and improve your writing even further. Take already made diagrams, how would you improve them? If someone asked for clarity on how to expand on that diagram (ie: how would an ISP fit into the HTTP diagram), what would that look like and what symbols and text would you use?

Another fun challenge to improve on writing is how would you explain (topic) to someone who is blind? It's more difficult than you think as we tend to rely so heavily on visual information, but it's a fantastic way to improve your skills by highlighting weak points in cross-type information.