I suspect it has to do with the animated geometric background on other non-blog pages of the site, like the homepage, and because the site appears to be a custom Next.js/Tailwind app coded by a college student and not a professional web developer who is used to supporting years-old browsers. (Safari has supported WebGL 2 since 2021.)

The websites uses a 3D library called three.js https://threejs.org/

If you go the main page of the blog, it is the background

https://www.mark-pekala.dev/

Why do you require using the IE of MacOS? Safari has terrible webgl support, and always has.