• Technical Skill Deficit-There are many developers available today who can execute a wide range of tasks in every industry. However, when it comes to blockchain technology, there aren't as many developers who have specific knowledge of the system. As a result, the scarcity of developers makes it difficult to construct anything on the blockchain.
• Network Dimensions-Blockchains demand a large user base. As a result, it is not as resistant to incorrect actions as it is to attacks and grows stronger. Because the blockchain is a resilient network with a widely distributed grid of nodes, reaping the full value is more difficult.
• Deficiency in security-A significant security issue known as a '51 percent attack' has been linked to Bitcoin and other blockchains. This security problem occurs when a group of 'miners' gains control of more than 50% of the computer power on the blockchain network. There is no centralised authority to prohibit miners from impacting the whole Bitcoin network if they gather sufficient processing power.
• Transaction speed and cost-Transactions were 'virtually free' for the first few years of blockchain's existence. However, as the network grows, it will no longer be the most cost-effective method of money transfer due to increased network transaction costs. It barely processes seven transactions per second as of the end of 2016, and each transaction costs roughly 0.20$.
• Mechanism of Consensus-You know that a block can be created every 10 minutes on the blockchain. Because each transaction must ensure that every block in the blockchain network reaches a single agreement, this is the case. The back-and-forth talks required to reach consensus can take a long time and resources, depending on the scale of the network and the number of blocks or nodes involved in a blockchain.

Read More: How does the security of a block works?