That's true for any teaching aid. Teaching is a hard, time-consuming process. The fact that some teachers have used Minecraft very successfully in their lessons

That's true for any teaching aid. Teaching is a hard, time-consuming process. The fact that some teachers have used Minecraft very successfully in their lessons proves it can be practical. It's up to the teacher to decide if they can use it practically in their lessons. Software tools (in general, not just Minecraft) could become a lot more practical in the future if the community creates a CPAN/rubygems/npm style archive.