A few times on a modded server I made an elaborate contraption of pipes and minecarts and whatnot, only to have somebody say "That's a waste of time, because there's this single block from this new mod that does all that for you." I mean really, by that logic the entire game is a waste of time!
Once a guy came into my house without asking me and started going through my chests. He didn't take anything, but he criticized the way I made my tools; I had a bunch of Tinker's Construct tools made of alumite and he said I should have made them out of cobalt. I said the Nether of that server was stripped clean for a radius of 500 blocks from spawn and I didn't have a good way of getting around yet. (Personal nether portals were forbidden; you had to use the one near spawn.) He just replied, "Use magical crops." Seriously? Magical Crops are insanely complicated and involved to cultivate, and what do you care if I make my tools out of alumite anyway? What do you care if I make a cleaver out of flint? Leave me alone.
That's why I made my own private server. XD