Saw this in recent updates, gave it a shot...
Generally, the battle system felt far too simplistic. You don't really have a deck or a discard pile; each draw just randomly gives you one of the cards you have equipped. And the card effects themselves are... pretty boring? Spend mana to do damage, or more mana to do more damage, or even more mana to do... even more damage. Or maybe you spend mana to defend or heal instead. There's just not enough going on here compared to basically any card battler to hold my attention.
I understand that this is an early demo, and things might change... but there's no need for three of the five cards in the starting cardset to be completely generic "spend X mana to do Y damage" cards. It's 2023; Slay the Spire did much better than that six years ago. Give the player a more interesting starting toolkit or you'll bore them to death. Granted, not every card battler needs to be quite as involved as Slay the Spire... but the game did redefine the genre, and not idly did many other card battlers copy the formula. You can certainly do different things than the StS developers did, but just doing less of them isn't enough.
As a specific problem, the way that cards both cost one mana to draw and reward one mana on discard is... kinda dumb? You can just keep discarding and redrawing until you have your desired hand, completely removing the randomness from the card game aspect. There are valid games that work like that, but if that's how the strategy is intended to work, you'd be better off scrapping the cards entirely, giving the player full access to all their skills, and letting them pick their moves for the round off a menu like a classic JRPG.