I believe only cards from 2014 or earlier have been required to be replaced so far.
People who had an octopus from the initial batch of 1997 could have used it for over 20 years and the deposit is still refundable, albeit with the aforementioned fee since 1.5 years ago. Meanwhile, many transport smartcards around the world have to be re-purchased every 5-10 years with plenty requiring a local bank account to get any refund of the cash balance
The OP's card didn't expire, but it became inactive after three years of non-use, thus requiring the payment of a fee HKD15 p. a. to reactivate.
However, it would still economic make sense to pay that money as long as there is sufficient deposit left on the card (on-loan cards start with a deposit of HKD50). Once the deposit has been exhausted the card can't be reactivated.