Brute forcing private keys is hopeless. What might be possible is recovering bitcoin from wallets whose passwords have been lost if the wallet file is retained, if the passwords are not too difficult to crack. And there might be bitcoins considered "lost" because the original owner has died, and whomever inherited their equipment has not noticed/found/deciphered their bitcoin wallet setup (or paper wallet tucked away somewhere). There are varying degrees of "lostness" to bitcoins that are considered lost.