The feature of being able to right click a block to get its colour was very useful. You could make camoflauge structures so that people wouldn't so easily realize you're making a trench or something right under their noses, and things you would make would be more visually appealing. I know this game is NOT all about aesthetics, but I liked being able to build a bunker that isn't gray and doesn't require me to look for colours in the menu rather than just right click. There are many colours that you can't access with the arrow keys colour picker.
The feature of drag and drop is okay, but it is useless. In that time that you're dragging the block GUI, you could just be placing those blocks, and you can't move it past where you're walking so there's no difference between it and the regular block placement. Its pointless, really, and I never see anyone use it. It saves a very very tiny amount of time, but I find that using it is more bothersome than just clicking.
So please return the feature of right clicking to select a block colour.
One more thing: There is a large problem with the spade that needs addressal. When you try to break a block and there's a teammate by, you hit the teammate instead of the block. Remove this so that people can work together building tunnels and structures and trenches and stuff like that. I missed being able to do that with the pickaxe in previous versions. :(