I really like hand-drawn diagrams from Apache Kafka and Confluent blogs and slides.
Most of them are done with a tablet without "fancy" software.
To do something similar in my presentations, I used an old DIN A4 Samsung tablet with Autodesk Sketchbook with good results.
I found very useful to be able to worki with layers, so I could draw the diagram on the top layer, and fill the shapes with colour in a layer underneath.
But the best part is I could focus on the storytelling, not in redoing again, and again the diagram in Powerpoint. With a hand drawing, you can iterate fast the concepts until you find it good enough.