Exaggeration is fun!
Yes, Minecraft, a game in which you can explore a constantly generating randomized world - within the limits of what it has available to generate, of course - is identical to a sheet of blank paper and a box of crayons. Everyone has the talent to make enormous three-dimensional recreations of their favorite architecture using only crayons and this simple wood product! Moreover, crayons will occasionally rebel to challenge you while you're drawing by hopping around the paper and butting into things! In fact, I'd call crayon AI even more challenging than-wait what?
No. No, that isn't right at all.
Minecraft is really more comparable to a game like Saints Row or Grand Theft Auto than a box of crayons in terms of "finding your own fun." Bear with me - I realize your first instinct is going to be to say "no it isn't you can't even build in those games and you have missions and guns and interactive NPCs and blahblahblah" yeah, I know, they're very different games; I'm not trying to say they're the same. I'm just comparing this one quality they have in common. See, when you've finished the "story" of, say, Saints Row 3 (which isn't really all that long), you're left with a reasonably big city and a bunch of tools you can use to navigate said city and blow its inhabitants to bits. There aren't really any
goals at that point, though. It's just a playset for you to mess around with however you like. Some folks will, at this point in the game, become bored with it and stop playing - they've beaten the game and don't see any reason to keep messing around. Others will use the options available to enjoy driving around the city, crashing into things, flashing people, swinging jets through narrows spaces between buildings for bonus points, fighting cops to see how long they can survive a full-on tank-and-helicopter onslaught before ending up at the hospital, and so on. Does this accomplish anything? No, not really; they're just having fun with the options the game gives them.
Likewise, Minecraft is a huge open world with a set of tools you can use to do what you want to do with it. What it lacks is the focus of a story or quests or similar objective-based gameplay (aside from the achievements, some of which are reasonably challenging to achieve, though a few are basically just luck-based missions). As in the above example, for some people this is a turn-off and they won't be interested in the unfocused gameplay available, while others will see this as an opportunity to have fun in their own way with the tools available. Could they do this with Legos or crayons or clay? Sure,
some of them could. Not everyone has the means or talent to create what they'd want to make in the real world, though. Minecraft is a much easier creative outlet for a lot of folks, and it certainly allows you to build on an incredible large scale compared to what is possible in reality (the Lord of the Rings recreation guys come to mind - seriously, I'd love you to show me how to recreate the entire Lord of the Rings world set anywhere near to-scale with crayons and sheets of paper; it's impractical even to imagine).
I'd really call it more "setting your own goals" than "making your own fun," though ultimately amounts to much the same thing. You aren't intended to "make your own fun" or "set your own goals" in Tetris, Call of Duty, or that other game you mentioned with the dribbling and paper (I'm afraid I've never heard of that one - is it by EA?), you're intended to go for a high score or get to the next level or follow the mission on your HUD or whatever the next pre-set goal dictates. Sometimes all you need is to have an open space to follow your own interests and see where they lead you. For a lot of people, Minecraft is a good outlet for that.
There's something important to keep in mind here: the fact that you (global "you" here, not an individual poster) dislike or do not understand the appeal of a given thing does not necessarily mean it is bad. It is completely okay to have your own opinion in opposition to others. It's okay to not like things! Even if other people like those things that you don't like! There's no need to wear yourself out trying to tear it down just because you don't like it; the people who
do like it are unlikely to change their minds because of a rant of dissatisfaction with X graphics or Y gameplay. Chances are they already know about these issues; they might even agree with you. They disagree, however, on the result of those flaws.
And that's okay. So relax!