> Minecraft [...] still have final bosses as well as achievements. You definitely run out of things to do eventually unless you just want to build stuff at the endgame and/or collect every optional item,

I don't know about Terraria, but only speedrunners consider the end dragon to be the final boss of the game. Besides the fact that the game has received regular updates with new content (and harder challenges/bosses) for more than a decade since the dragon was added, it's a block game...

> unless you just want to build stuff at the endgame

That's like saying "unless you want to build things with lego." Building things is the point, it should go without saying. Beating the dragon is what players do in the first day playing on a new map to clear the way for the real gameplay. It's a prerequisite (not finish line) for getting a full set of equipment so you can start building in earnest. Beating the ender dragon is like getting the box of legos open and poured onto the floor.

In Minecraft, Survival Mode is the main thing. While you can still build, of course, and you likely will to create a base, I would not say building is actually a major part of the game anymore. Comparing to legos feels a bit off. I played a lot of Minecraft, thousands of hours, a fair bit of that was with mods. A run just tended to peter out after a few weeks. I'm not saying you'd stop at the Ender Dragon either, but once you've done "all the stuff", it's often more fun to either start over or play a different game for a while. I know when hosting servers for a dozen or so active players, most people didn't stick around more than a few weeks, and often they'd ask for a "reset" at some point because the early-game progression was more fun than having a bunch of endgame stuff and not much left to do. Terraria has a much larger focus on combat than Minecraft and many more bosses and clear progression, but I still think of them similarly here. I don't have some 15 year old Minecraft map/server, I have many distinct memories of playing through the game for a while with different people at different times, starting over is just part of it. That goes for Terraria as well, it's borderline taboo to bring a character with progress into a new world if your friend is starting a new character, and if you both had endgame characters it just wouldn't be that interesting. While a speedrunner might skip a lot of the game's content to get to beating the Ender Dragon, a more typical player would probably just get a good mine, good farm, good stockpile of crafting materials, maybe upgrade/rebuild their base once or twice, and eventually not have much left to do. I know there are people building computers in both of these games, but as far as real world cases, almost no one I know even touches Redstone beyond the minimum. I see these more as adventure/sandbox games than building games, even if you can build. I do more terraforming and spelunking than building things just for the sake of it. Expanding your base is often to fit more chests or in the case of Terraria, because you need more places for NPCs to move in so you can access new shops. If building things was a major goal of yours, then it certainly gets easier once you have upgraded movement and mining speed and so on, I just find that I/we usually stop playing around then.