Thanks for the prompt response,
@Major Crimson. It's not the hosting; the test image you posted is exactly the same as the original. The issue is that you have to change your browser's zoom to a readable level
before you take the screenshot, since images are static and not adjustable.
But to be fair, taking and uploading a screenshot as big as this turned out to be an absolute nightmare. The one Chrome add-on good enough to take a decent-resolution screenshot of your Sandbox article link, GoFullPage, split the image into four parts; I had to stitch them back together using Photoshop, then reduce both quality and resolution by 50%. And finding an image host afterwards was basically impossible: Imgur and ImgBB automatically reduced the resolution so much that the image's unreadable; MEGA, Dropbox and Google Drive are all incapable of previewing because the image's so large; and Google Photos flat-out refused to upload the image (I have no idea how you got Google to allow your original image to be previewed in the first place).
I spent an
hour on this before I gave up finding a host capable of previewing; here's a
Dropbox link to download my version, if you're interested. Ultimately, creating
multiple Sandbox subpages on Wikipedia (one for each article) is far less work than trying to take and upload a full-page screenshot.
Oh, please don't be discouraged on my account! The wikipage format is itself excellent worldbuilding - the article would have been less impactful had it been a standard text post, so don't worry about creating a text version; having the Sandbox link is more than enough.