It is up to you what is your endgame content some people endgame content is getting all items to pen, Getting a carrack, reaching top1 at all aspects fishing,cooking,alchemy etc.Some even consider having top 1 points in house decorations endgame . The fun to it is that it's endless and you're the one making content. 

this question relates as well to the Guild you are with. Of course our circles of friends. Our guild have many supporters in it, so we try our best to motivate each other to come out with guides and encourage others to join in. My group of friends is always on Heidel 1 server, playing music n doing stupid stuffs to laugh at. Your game, your way. have fun!

To add to what other people have already said, for some players completing ecology and adventure logs to increase their energy is also end game content. Some players like questing to reach milestones and increase their contribution points. Others want to have the biggest node empire in the game. Then some focus on sea content like sea monster hunting and barttering. There are several routes you can take when it comes to end game content.

I think this is different per player, it's a case to case basis. For me, I don't do pvp and hate grindig, so I focused on knowledge which gives me more energy, which helps in my Lifeskill. I used to have 200+ energy for a long time, now I'm 500+, just by folloing the knowledge tracker H. Making silver is another end game for me. To balance out the RNG, i want to have a lot of liquidity so I wouldnt have to worry about enhancing gear. And lastly, housing and fashion. I'm currently collecting all the outfits that I find nice, meaning I wouldnt buy an outfit just for the sake of collecting. For housing, I will work on getting more CP to get a huge house in Grana where I can put a lot of furniture. More room, means more space for stuff, means more time to decorate = more fun... for me.