According to my profile, I created this forum account a year ago XD. I guess I just happened to be looking in the right place at the right time to see your post and to already be watching and reading about game updates through the years and have at least dipped my toes in all the game modes to feel like I know what is going on.
I think they made a smart decision to have the level cap at 80 and just move into the mastery points system to extend playability (though the game doesn't really spell it out for you that once you hit 80 your exp bar is still working even if/when you complete mastery tracks!). Personally, level 80 feels more like the real beginning in terms of gameplay and 1-80 was the re/introduction to the Guild Wars world, especially because it's just not a grind like in other games.
In terms of end-game content, there is obviously only so much story at a given time between expansions and mini-expansions/Living World stories, but there are so many ways to play GW2 past level 80.
Even then, the way they have implemented PvP and the WvW modes gives you whole new ways to play that makes it accessible for mostly PvE players like myself to get into PvP and WvW, casually or not so casually, and also makes it useful for PvE play (ways to get gear, items for legendaries, alternatives to gaining hero points, and all that jazz). Not to mention the sprawling dungeon system for group play — regular dungeons, Fractals, Strike Missions/Dragon Response Missions, Raids. Also, it can't be understated how important guilds are and finding 1 or 5 to join really does add to the gameplay, including game content that helps in PvE/PvP/WvW. Then there's the achievements system which gets weaved into all game modes. Add into that the fact that the devs regularly rebalance classes and mechanics so that keeps things interesting in all game modes, not to mention the various classes and elite specs you can get into.
There's just so many layers to the game that encourages exploration so that even having logged into the game daily for over 2.5 years I still feel like I've only covered a fraction of it.
But of course, the real real real end-game is *Fashion Wars* (and maybe decorating) so if you're not into that, you're not into that.