Disadvantage of blockchain

Complexity

Blockchain technology is not fit for mainstream yet. With terms like SHA-256, Proof of Work, Proof of Stake, Nonce dominating the vocabulary, it needs to go through the process that the internet did. You are comfortable using the internet without really concerning yourself with TCP/IP, HTTPS, switches etc.

Network size

Blockchains are only as strong as the network size. The larger the network, and more change to get attack.

Human error

Blockchain can be thought of as ‘garbage in, garbage out’. The data going on the Blockchain is immutable, permanent. If the data stored on the Blockchain is inherently untrustworthy or inaccurate or riddled with errors, there is very little Blockchain can do about it other than holding the garbage unchanged forever.

Unavoidable security flaw

There is one notable security flaw in bitcoin and other blockchains: if more than half of the computers working as nodes to service the network tell a lie, the lie will become the truth. This is called a ‘51% attack’ and was highlighted by Satoshi Nakamoto when he launched bitcoin.
For this reason, bitcoin mining pools are monitored closely by the community, ensuring no one unknowingly gains such network influence.

Democracy/Politics

Where there is a democracy, there is politics. Blockchain networks tend to be governed by developer communities following their own written and unwritten rules . They do not have structured structure.