Most classes basically had the same combos since the making of the game in ARR, and probably even before that, in 1.0. Why not give us new animations?
MCH in 3.X had some underwhelming attack animations so they fixed them and now they're pretty flashy and it feels good to use their skills. While you have MNK who is a very combo based class, still stuck to some very old and weak looking skills.
They even took away some good stuff like Ring of Thorns and Wide Volley and kept Doom Spike and Quick Nock instead (I don't mind Doom Spike mind you). Upgrades to the moves animations would make them feel more powerful and fun to use, and make being at 70 feel awesome.