The problem might be due to antialiasing applied to the wrong font size. On my desktop the page is easy readable, but some letters have their vertical lines appear as two grey lines instead of a single black one or a mix of the two, in other words although it's 100% black text, the antialiasing renders some parts of it like 50% black to make it appear smoother. On a phone it might be even worse. Changing the font size can help.

Not an expert in anything about web publishing or similar stuff, so forgive if I used the wrong terms.

Here are 2 screenshots from Chrome on Android displaying the article. The one in the left is how your article looks by default. The readable version on the right is how it appears when you accept Chrome's offer to show a "simplified version".

https://photos.app.goo.gl/ntvIcKSDTOfdkwAi1

When you're picking colours you can use an online tool to test contrast against accessibility standards.

Your inline code parts still meet the double A level of the accessibility standard for contrast.

http://leaverou.github.io/contrast-ratio/#rgb%2882%2C89%2C93...

It's not the color, it's the font that has too thin stems which can make it look grey depending on anti-aliasing and font hinting settings.

It is worse on mobile firefox: https://imgur.com/a/WgS3d

As others said, the problem appears to be with the font. A child comment of one of your sibling comments linked to a side-by-side comparison of how your site looks (left) vs. reader mode (which I forgot about when trying to read the article): https://photos.app.goo.gl/ntvIcKSDTOfdkwAi1