What happens after getting clearing tier 5 quests?

Hi guys, my brother and I are playing just the two of us on our own server and having a ton of fun with the game. It's been one of our favorite games ever. Both of us are motivated by overcoming the games obstacles rather than being pure sandbox enjoyers. We got to a point where we can easily handle tier 5 quests and blood moons are also pretty easy for us with the awesome base we have. Are there other challenges or obstacles remaining in the game or is that the end for us?

Also I heard there's a big mod called darkness falls. Do you guys have advice for adding longevity to the game in the form of mods or things we might not know are in the game?

Something we found kind of disappointing is we haven't even unlocked rocket launchers or late game vehicles yet but it seems like we're already kind of dominating the game and there's no use for those?