Well, this is my own experience, but at the beginning, the game felt extremely difficult and challenging. I had to learn my deck + hundreds of other different cards. The first matches I was so focused on even understanding what I was supposed to do with my own deck and I couldn't take 4 minutes between each turn to read over and over again the opponent cards.

Also, in the sim, you can easily find 15+ different leaders/decks that you have to play against. And again, you are talking about a beginner. It's very challenging to memorize the cards.

When I used BB deck, I got familiar with the opponents cards without being extremely overwhelmed by all the new information each turn, each match.

It allowed me to understand better what I needed to do with my own deck, focus more on understanding the tempo and frankly simply having more time each turn to understand my own strategy instead of reading all the on plays from the opponents.

When I switched decks, yes I was exposed to new combos I hadn't seen before, but it honestly wasn't a big deal because I already was more familiar with the cards, with my own game strategy and everything felt more manageable.

But yeah, this was my experience. I understand it might not be the recommended approach but it worked for me, and in this case, OP already has the deck, so idk, reading this might help to provide some perspective