In general, cards are needed to use them during rebirth. And those cards that are not used in this way are immediately automatically exchanged for gems. Where did you manage to find the unnecessary cards? :)
Ok. I will answer in detail.
1) I agree that the excess of something that you got through hard work is annoying. You've been working so hard, and now he's just lying there useless. It's infuriating!
2) "It's going to be good." Alas, this does not work in game development. No one knows if an idea will work or not. Completely incomprehensible things are gaining popularity. If there was a way to predict this in advance, we would only play super popular games :) So you actually said, "I think it's going to be good." And this is the opinion of a single person. No one here supported you. It's just a fact. Without ratings.
3) Personally, I think it would be much better if the game got more content, rather than ending abruptly like a behemoth :) Between a strange unverified idea and a thing that prevents absolutely every player from playing the game, anyone will choose the latter, agree :) But the author has not pampered us with updates for several months now. It's not up to your ideas anymore. To get what you need, we will think about what we want later :)
Update:
I've thought about your idea some more. In order for your proposed mechanics to work, and not just be a strange way to delete cards, you need to constantly buy new useless cards. Do you have any gems for that? Does anyone have one? :) Emeralds, when they appear, can always be spent on treasures. Of course, there comes a point when it becomes pointless to spend them there, but by this point, believe me, you absolutely don't care how many extra cards you have. Check out the discussions below. The Horde, for example, passes under very specific cards. No one cares how many extra cards you get while you're mining these. If one rebirth lasts for six months, you will have more than enough emeralds for it :)
thank you for explaining this better for me.
Answering your update, i had been trying to get backpack check for future runs and to complete deck collections and it made me work for more to get emeralds faster to get the duplicates i need but duplicates that i have plenty of just kept stacking.
Again, thanks for helping me understand and i hope that we can better understand our issues or suggestions within the next update. (: