I think Minecraft is one of those things you either like or you hate. I can fully understand anyone who would dislike it and why.
Minecraft Classic is just a small taster, it doesn't do the full game justice at all to be honest. For me survival mode is the highlight so far, exploring a vast and endless world, at your own peril, that is all for you.
Really I think it has a lot to do with what attitude you go into the game with, a lot of people hear about it and hear that it's popular and expect something exciting. It isn't exciting and it isn't gratifying, there's no goal and no scoring (yet). So they find it boring, and it will be boring if you're not in the right mood or if you're expecting to have an exciting experience. Totally understandable, I get bored of it often. In fact it's one of the few games I play on a casual basis.
But it's a marvellous timewaster, an endless and quite adorable world generated on the fly, sometimes it can be just the thing if you stick on some relaxing music and just do your own thing in it. - Providing you have time to waste.