What I like about Holy Week liturgy is that it is SO OLD, it makes our beloved Tridentine Mass seem like a "novelty"!
The fact that during the Adoration of the Cross we sing "Hagios O Theos" and then translate it for the peanut gallery into LATIN "Sanctus Deus" should tell you something about how old it is -- it dates back to when Latin was the vulgar tongue!
And notice that on Holy Thursday the Mass is a bit different? That's because they didn't "add anything" to Holy Week, even as they added things (good things of course) to the Tridentine Mass.
So you have a liturgical time capsule from the earliest days of the Church, more or less.
Yes, that's pretty awesome.