Blockchains are very cumbersome technology.
The idea of keeping record of all transactions from first to last leads to growth in size and at some point this becomes a burden which fewer and fewer nodes can carry.
While at the present time people focus on the money and value floating around blockchains they miss the fundamentals.
Blockchains brought up the ideas of decentralization. But at some point people will get tired of hearing about blockchains.
They will probably be remembered as an intermediate step towards decentralization.