>holding down the mouse button to mine

And football is just kicking a ball in a pitch, and racing games is just going in circles in a track. Obviously there's more to it than that simplistic reduction. In particular, you have to think where you mine, how you organise your explorations. Then, you can run into myriad things as you explore: caves, water, lava, dungeons, monster spawners, many types of ore and rock...

And if you don't fancy that and just want the equivalent of a bottomless box of legos, just fire up creative mode.