My suggestion is that mtg arena should include all of the cards printed that are legally playable in real life. Consumers spend countless hours tweeking and building their decks in real life and im sure would love to be able to put their exact decks on the arena to play with others world wide instead of having some cards kept out. Just as a example, Sol Ring is not available in mtg arena. That card is printed in so many different sets and utilized in the real world competitions heavily. So why exclude it from mtg arena? I understand you are trying to make the gaming experience fun for everyone but part of the greatness of mtg is being able to build your own deck and tweeking it to be really synergistic. If people can't understand that you won't always win then maybe you could do a bracket system on things like brawl. So that way you can choose any card that is available to be used in real life and build your deck exactly how you want it to run instead of trying to substitute cards because the card you need isn't in mtg arena. So if someone is running a bracket 4 deck then they can only play that deck against other bracket 4 decks and so on. Then whatever play level they are at they can have fun and not complain so much and the people who like playing more competitively have the opportunity to do so and have access to all of mtg's cards. I built a bracket 4 elf deck and over 20 cards i couldnt put into my deck on mtg arena which seriously changed how the deck works. I did what i could to substitute but sometimes you just need a elvish branchbender. That's just a example. I love this game and I love the idea of mtg arena but the fact that you are purposely keeping cards out is seriously hurting the playability of the game the way it was meant to be played.