RFID wallets do not ruin credit cards. RFID wallets are made with materials that block the RFID signal from credit and debit cards. The card still puts out the signal, but the wallet’s materials prevent the signal from leaving your pocket. This makes it more difficult for anyone to skim the card’s information when it is inside the wallet.
Because the wallet’s RFID-blocking technology doesn’t actually affect the card’s ability to put out an RFID signal, it has no impact on the card at all. If you take the card out of the wallet, it will still put out a readable signal.