Itemlevel should be an indicator of what type of content you do, and for people to see if you know how the mechanics work in the raid. With titanforging there was an ilvl inflation that made it harder to gauge what your capabilities are.
It was one of the many reasons why raider yolo became so popular, because player ability cannot be reliably gauged from itemlevel alone. WF/TF isn’t the only reason, but it is one of many.
As a raider I had one occasion where I received a titanforged Font on the first run of my mage, while the other mage in our guild had to go back to EP for 2 months straight to get one for himself. He felt incredibly annoyed by it, and I felt incredibly sad because he was playing way better than me (having played mage far longer, while I only started playing mage in 8.3) so I felt he could have gotten more out of the trinket than I did.
The game needs set loot progression, and uncapped WF/TF is actively working against this concept.