The main feed has infinite scroll on the main feed (I am not especially a fan of that). When you click a link it is a popup over the top of the infinite scroll page. Close the popup and you are at the same position in the infinite scroll list. I didn't like the new design at first, but after using it for a bit it's not that much difference. The low quality of posts combined with heavy handed moderation is far more of a problem for Reddit than the UX.