Of course, there will always be the one person who goes on this long drawn out talk about how you don't really win Minecraft
But the objective of MC is have fun, build, survive, and explore.... The ender dragon seems more like a side-quest if you think about it...
Minecraft is like GTA you beat the campaign but it let's you control nue after ward so in essence you Beatty game.
It's not actually possible to complete a sandbox game as theirs always an objective to do. You cannot actually complete MineCraft, you can beat goals and force the credits to roll, but you will never finish the game .