Warforging is reasonable. When you get an item it has a chance to upgrade 5-10 item levels, this is reasonable RNG and when it happens generally players are pleasantly surprised.
With Titanforging, it gives players unreasonable expectations that causes behavior of players wanting MAX itemlevel groups to carry low level keys- because there are suckers who will gamble away their time to try to get that item that they are farming to titanforge 40 itemlevels, thus shunning players who are appropriately geared for that content.
Player item level inflation and ridiculous demand of overgeared players for trivial content is not because of the availability of M+ keys, but because of the titanforge system. Do you think doing LFR which gear is base ilvl 860 should reward a player with ilvl 900 gear purely because of RNG?
EDIT* A lot of discussion of when it comes to Titanforge becomes who deserves what gear whether it be mythic raider or LFR hero or M+ devotee vs time invested into the game. Overall, I think we can all agree that Titanforging has caused a massive amount of gear inflation vs perceived player skill and drives lower ilvl characters to EXPECT high ilvl players to carry their lower level keys. This is because there are many that desire that chance to titanforge a specific item they are farming for- thus increasing the amount of high ilvl players that are willing to do these "carry" runs of lower itemlevel key, thus taking that potential spot away from someone of lower ilvl who is also applying to that content.