> but do you really expect a review process to identify that a diagram is a copy from another one some rando already published on the internet years ago?

We aren't talking about just some random image from some random blog. The article we are talking about is about a specific topic, which when searched online one of the first is the article containing the original image (at least for google, bing seems to be really struggling to give me the article but under images it is again the first).

I would cut some slack if this were a really obscure topic almost noone talks about, but it's been a thing talked about in the programmer space for ages.