At a certain point, you will get stuck because you can't get enough papers and parts to open the forest, and if you don't harvest truffles, you can't send half of the plane orders or most (if not all) of the train orders. So therefore, you can't earn enough gems or get paper drops to open the truffle forest.
Those that pay for gems to expand or those who had a stockpile of papers right before the upgrade are probably still enjoying the game.