Can you explain this using different words than the ones you already used?
I am not sure I quite understand. What is the problem with the sideboard cards and the sleeves?
Thank you <3
They frequently get mixed into the deck, they require a surprising amount of extra thinking by both players to understand the board state at any time (especially with multiple token types, which is common), they're easy to mistake for your hand or the person next to you's hand, and they make a visually messy board.
It's simply not a pleasant play experience imo. It works, and it's honestly fine - I fully acknowledge I'm being dramatic and this hasn't caused many issues that couldn't be resolved nearly immediately -- but gameplay feels so much tighter and proper all around with the physical tokens being called for that are easily distinguishable, tappable, etc.