Due to the way the world progresses, it's frankly a bad idea to join random servers. Play solo or play (together) with a select group of friends in a coordinated game. I actually think that "join randos in a public server" should not be an option because the game doesn't support it well and it can pretty easily ruin the game for you.

Basically the game has some random base attacks (and, later, basically assassination attempts on your person) that are unlocked as someone (anyone) hits certain milestones in the game. You could join a random server that has already finished the last boss and now you're getting attacked by plains goblins out of nowhere at random because that's what stage the game is on, even though YOU are solo and new.

There's also lots of griefer potential. In summary, don't join random servers. This is a solo / cooperation-with-friends game, not a random server join game.