Quote from d3fin3d
TL;DR: Has Minecraft been rushed to completion? Has The End been half-heatedly conceived and implemented? Is it too limited for an 'official release'? Should the energy spent on Minecraft have gone into adventure or the original ethos of the game, sandbox+landscapes+mining+crafting?
The arbitrarily selected "release date" prevented a lot of important polishing from happening. It would have been much better to select a list of features that needed to be finalized and when nearing the completion of that list to plan for a release.
Of special note I would say the world building code should have been polished up much better than it is so that content released post launch would be backwards compatible. Every significant change to that portion of the code flatlines old worlds and forces resets of multiplayer servers.