AoE3 is a game with a high learning curve. Especially since there are so many cards (a good part of which are off the meta). So because of this, new players can be overwhelmed by the number of new cards out there when it comes to creating an efficient deck and have to go through guides.
This is too complex so I would like to propose that each civilization have two decks (completely competitive) by default (similar to the LoL runes, where you can create your own but then there are a series of “decks” by default).
Thus, as soon as the new players started, they would already have two decks of cards (perhaps one oriented to the early and the other to the late) and as they gained experience they would develop their owns.
PS: I was not going to propose this because I have the feeling that developers dont see these forums but anyway.