I am very interested to know if cryptocurrency wallets like Bitcoin Core, NEON, Electrum can ever be hacked ?
definitely yes, but it is because of the users end not because the of the wallet perse especially if your wallet is decentralize, hacker entry is throough emailed phising site, or crack app downloads with malware, or visiting suspicious websites etc. so you you to be very carefull.
I will prefer to use hardware wallet like ledger or nano wallet as they are cold storage's and most secure. Since they are offline wallet and no available online, no one can hack them.