I struggle a lot with this in my work. I can’t assume that my readers are fluent English speakers, nor that they understand the topic. I can’t even assume that they care to understand. I have adopted a plain and unambiguous writing style that hopefully accounts for it. I am now experimenting with formatting that allows them to skim everything and still get the gist of it. In my opinion, nhs.uk is the best example to learn from.

People are not stupid, but they are busy, tired, lazy, or simply not that interested in the finer details. There is a balance between respecting their intellect and respecting their time.