Cards that steal from your opponents deck are toxic and not fun
Cards that steal from the other player's deck are NOT FUN to play against. Breach the Multiverse, Etali Primal Conqueror, siphon insight, etc are some of the least fun cards to play against. Make people craft their own interesting decks with powerful cards. Being killed by your own win con feels ******* terrible. When someone mills 10 cards or exiles the top cards of my deck and then kills me with my own win con I just stop playing for the night. This is a **** mechanic that feels terrible. The whole draw of standard is to understand the meta and craft a deck with tools you have to counter what others can do. Just milling the opponent and taking whatever good stuff they have is a good strategy it takes all the thought and interesting play patterns out of the game and says "counter this or die to your own stuff" which is really really not fun.

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YawgmothReborn#93109 commented
Resurrecting old thread...
Agree wholeheartedly op. Since your comment wizards has doubled down on making cards that steal. I see no chance that this ends anytime soon. Wizards has shown time and time again that they will not listen to feedback from players. -
Deep Thought#64644 commented
I would generally agree with you that effects that steal cards from your opponent's deck are not fun cards. Wizards has been printing more and more of these cards, with effects that allow primarily red, blue, and black decks to cast things from their opponent's deck. This mechanic does not lend itself well to paper Magic at all, as it often results in unreturned cards.
I do hope Wizards rethinks this path.