In other words, you need to login to see the board now. This will help
increase registration count because everyone loves memes and shitposting. reduce the amount of weariness from new members attempting to join the community. Yes, viewing shitposts is now a privileged right in which you need to register to get that privilege. Want to shitpost? Work for it.
This will also remove off-topic discussion from recent posts if you are not logged in.
In the event that you want to remove off-topic discussion from the recent posts completely, nolem has written a script
here that should help you with that.
I believe this was also how it was at the old TF2Jump forums. Don't remember exactly, tho.