Not sure if you’re still having this issue, but I too was unable to shift click people’s names in chat / shift click items in my inventory to split stacks / ctrl click items to see them in the dressing room. I tried deleting addon / WTF folder - no luck.
What DID work, was going in to the in-game Key Bindings menu and unchecking the box for “character specific keybinds”. It said all keybindings would be erased, but low and behold, all my keybindings were fine (your mileage may vary) and I could now shift and/or CTRL click like normal.