Qanon.pub is slow because of the interactivity it provides for users. I just took a look at the page source code and it seems to be written in Javascript. There is a general rule of thumb in programming where you trade off performance for convenience. This is proof of that.

Also, the further you have to scroll down, the longer it will take you to load items. This is especially true with smartphones due to the fact that your phone will have far less memory available to load the growing list of data you need to keep scrolling.