When threaded view needs to open every message in a new page, it's really inconvenient, and everyone would prefer linear view where you can see several messages at once. The downside here is that you need to quote, and besides, long threads don't fit on one page.
However, in the link I've provided you enjoy the best of both worlds: the threaded view that allows you to follow the thread development, as well as seeing everything in one page: once you click on the subject line the message opens in-place. Click again, it closes. You can open as many replies as you wish, or close all of them with a single click. You can see immediately the replies you haven't read yet, they are 'drawn' by slightly different color. (No need to perform Search for new, which is a burden on a server.)
This one certainly isn't outdated!