I think Whales would like it as their rare expensive cards would get a bigger cut of the entry fees and Farmers by default are a negative for the game since they only really aim to extract value. This likely will be a problem again once survival mode goes live.

I actually added 4 more reasons

Everyone Can Enjoy All Existing Cards!: Right now, most players never will get the excitement and fun of playing with the most powerful cards let alone at max level. This while there are many cards that nobody ever plays. With in a game mode like this, all cards actually get a proper use case in the actual card game that everyone gets to enjoy for the same entry price.

Counters Power Creep: One of the main issues in Collectible Card Games is that there is not only an incentive to print more cards but also to make them more powerful. The ultimate showcase of this is the current Heloise The Hollow auction. A game mode like this would counter this power creep and make it more a luck RNG factor since everyone has equal odds to get good or bad cards. As you face off against opponents who have similar win-loss ratio during their run you either will face players without or with the powerful cards leveling it out.

More Conclave Arcana Sales: As the new set is released, the new cards from the start could get implemented into this game mode. This means that there is a bigger incentive for players to buy packs and get the cards to max level as fewer of these cards will be in circulation compared to existing sets. So the entry fee cut for them will be higher. This also goes for existing Soulbound cards which have a high premium to unlock, there would be a proper incentive to do so.

Always Fresh Gameplay: Right now, players have the cards that they own or rent and are pretty much stuck with those. Most of the time it are also just the meta cards that are played which gives repetitive gameplay. With a game mode like this everyone would constantly discover new cards since there are already so many different ones in the game which will keep it fresh for longer time.