In theory the BTC Blockchain is not unhackable, but we need a hashrate of at least 51% on the blockchain network, so that hackers can control the blockchain to their liking. At least it takes the combined power of the 5 largest mining pools to be able to achieve a 51% attack. Although now the Stratum V2 protocol has been embedded. but this protocol is cryptographically signed by a large Mining pool. To carry out a 51% attack on the Bitcoin blockchain requires an hourly fee of around $ 770,000, what if this attack fails, will hackers not go bankrupt, so you have to think twice.