Not just you. For more than a quarter century, we've known that if a paragraph's text lines sprawl across a wide screen, it's more difficult for most people to read. (And the same is true if the lines are too short. There's an optimal range.)

https://jamesmattison.co.uk/method/why-line-length-matters-for-legibility/

For this reason, it's good for a website's style rules to limit how wide (measured in characters) a column of text can get, regardless of how much screen there is to expand into.

On desktop you can change window sizes to what you want. Don’t like wide text? Use part of the screen. But the inverse is not true: if a site decides to stay skinny you can’t make it wide if that’s what you prefer.

This is why I miss square screens. And I miss proper UI/UX design which makes good use of screen real estate.

If you don't want to change the window size for whatever reason, I find that reader mode (F9) solves this problem pretty well.