There's truth in that. I was thinking of giving higher tier tiles different shapes or making the player always drop two tiles at once. My friends said this version is hard enough, so I kept it this way. But I see your point, it very much becomes sorting when you're good at the game. What would you like to see to make it better?
To be honest, I don't see a way to directly improve upon this falling tiles approach. Being able to manipulate the "scenery" on the inside, or maybe something like the 4096 gameplay could be interesting, perhaps combined with some kind of synergy mechanic where certain tiles give you bonuses when they are close to certain other tiles (though the amount of synergies can't be too high, or the calculation gets too annoying).