Years ago I bought on impulse a game where you had pre-constructed deck that you cannot modified.
I think that the game had about 6 different decks. I bought 2 to start with and we had so much fun on the first night that I bought the rest on the next day.
The game was called Fight! and it was a French edition of a game called Brawl by Cheapass games: https://cheapass.com/brawl/
We really had a lot of fun of picking a deck and playing a few games with it to learn its strength and weakness and then to exchange the deck with your opponent.
If KeyForge can give me the same feeling, I am sold and will surely buy a few decks to play with friends.