1. Scalability
If the blockchain network processes a large number of transactions per second, we refer to it as scalability. From my research, I see some points as big challenges to blockchain, like if the network got congested, there would definitely be high transaction fees, and scalability issues can limit widespread adoption of blockchain technology.
Many altcoin blockchains with very big block sizes but they don't have too many users and altcoin blocks are not full. People are intelligently enough to choose good blockchains to use, it's Bitcoin blockchain.
2: Regulation
This is also one of the significant challenges blockchain technology is facing because a lack of clear regulations can lead to confusion among the investors and other businesses, and if the government cannot regulate the blockchain and cryptocurrencies, it can also result in reputational damages and penalties; the risk keeps increasing.
Governments if read your post, will like it, because they love regulations. I can use Bitcoin blockchain without scams, and I don't need regulations from governments to achieve it. People are scammed because they are careless and regulations from governments can not help these people.
Regulations damage our privacy while with careful people, they are not victims of scammers, so why do they need regulations that destroy their privacy.
3: Consumption of Energy
An example is bitcoin, which uses or requires a significant amount of energy to power its operations. The consumption of this energy can lead to a limitation of scalability, as the network may not be able to perform a large number of transactions.
Debunk this fud against Bitcoin blockchain.
Debunking the "Bitcoin is an environmental disaster" argumenthttps://endthefud.org/energy4: Complexity
If the blockchain technology is complex and difficult to understand can leads to adoption because individuals and businesses can not continue invest in something they are not understanding fully and complexity can also lead to errors and risks, the increase of high risk and errors can cause reputation damages and financial losses.
It's not complex. People lose money because they are careless, not because of blockchain complexity.