When coming up with formatting for a website, there's a real hobson's choice - light text on dark background, or dark text on light background. It's hard to say one is objectively bettern than the other, because there's a decent number of people who struggle with each.
However, you can use a "bookmarklet" to deal with pages that are the wrong sort for you. This is a small piece of javascript code - the same sort of programming that handles dynamic stuff on most websites - that you put as a bookmark, and the code will run on the page you are looking at. Just drag a link to the code to your bookmark bar, and you will then have a button that will activate the bookmarklet any time you like.
So, here's a bookmarklet for changing text to black-on-white: Make black-on-white
Just drag that link to your bookmark bar, go to the page you want to read, and click on the new button. Maybe try it out on this page.
There's also a link with the same effect below my profile, either on the right on desktop, or below page content on mobile. Click that while looking at any part of the blog, and it will make the text black-on-white.
