If you like Vanguard the card game, you will like the 3rd season.
If you are like me, who walked into this series w/o knowing any of the card game rules (and actually don't care for the vanguard franchise at all), you wont like it.
I praised the first two seasons of the show because of its ability to write an emotionally gripping narrative despite using a card game that I didn't know anything about as a vehicle for the story. I think the third season really suffers from focusing on the card game itself and being self absorbed in this tournament thing. That was never the interesting part of the show... so, I am quite disappointed.
This arc was extremely weak in terms of characterization of the new main cast. The new girl, Urara, is just a genius and that's it. She's shy and gets super focused while playing the game but it is super lacklust the way they characterized her. Other participants are also very boring with the exception of Michiru and Raika. I like the fact that they have some sort of connection to each other that does not involve the main character!
The other thing that I really liked is Yuuyu and Mirei's heart to heart about representing their teams and being a leader. I thought that was rather good. She's the best character in the whole show imo....
Anyways, Vanguard fans, you got what you wanted. A show about the card game itself.