Cards differentiate from other game pieces in that they can be face down. This allows for two main mechanics that games leverage. The first is a deck you can shuffle. This produces a random element from which you can draw from and this makes it so rare powerful cards can exist in a balanced environment so they aren't constantly winning games on their own. The second is secret knowledge. Card game players receive a hand which is their cards to play when appropriate but the other players do not know what is in their hand which adds intrigue and allows a layer of deduction based skills.
I've been around since the beginning of Splinterlands and I have a good sized MTG collection. What you're defending is not a beneficial feature to me. Cults exist all over. A lot of people believe the earth is flat. Just because someone puts faith in something, does not a valid argument make. Splinterlands isn't the worst game ever. It's just rock paper scissors with extra steps and they really dropped the ball folding card game qualities into their "lottobattler". That's why they pull people from gatcha games and not from "other" card games. Maybe things will be different when they add in the items and spells but I'm not sure that's complex enough to make a substantive difference.