I disagree somewhat with the idea that it's all the same after the first few minutes- once you start unlocking upgrades, the vibe of the game changes a lot. Multi-draw not only makes your life way easier, but also adds a nice new layer of complexity by letting you move cards from one pile to the other to get to ones that you buried before- makes drawing new cards much less of a commitment. Automation changes everything again too, so the new gameplay becomes figuring out how to optimize the auto merging by moving certain cards from your hand back to the deck, making sure the auto doesn't get stuck with a hand of nearly unmergeable cards. Game becomes extremely fast at that point, but that's honestly a good thing, since, yeah the game gets repetitive well before then.

If there's one thing I think the endgame needs, it's a way to easily reduce the amount of junk cards you have- specifically because of the challenges. Like, adding a "sell all 1 stars" button would make it infinitely less of a slog.

During challenge 3, I didn't want to individually click and sell every low rank card, so at first I tried to actually merge them- that was a mistake. A LOT of time and effort for very little gain. Eventually, I just decided it was easier to let my deck become extremely bloated and just click the draw button hundreds of times. A way to easily cut down on the deck size and get rid of useless cards would've saved me well over an hour of frustratingly tedious gameplay. Challenge 1 and 2 were fine, but challenge 3 was just too much.