It's good rogelite but I would, remove the power up cards from the starting selection of cards, and if posible make imposible to pick the end round card. so the player has to at least try to beat one stage with enemies.
The bigest issue it's ever the end round card appear you don't have reason to not pick it literally, skiping rounds and that is a thing you don't want in a roguelite, there is no reason to risk as the "power up" cards only last a single round, whould be intersting if you can stack them in some way to the upcoming round. and that go in counter of the core of you game loop, you need to find a way that pick or not the flag card be an strategic choice