Well…TW dungeons were harder before, but they’ve since been nerfed somewhat recently. Noticeably, the TBC dungeons. Wrath almost seemed to be harder, but probably the same difficulty, just harder than the nerfed TBC ones.
I like being able to go back through old dungeons solo and steamroll everything in sight while hunting for collectibles, doing old dungeon quests, and working on old achievements. Don’t take that away from me. (Timewalking is fine.)