But what we cannot do is see all transactions details, such as the transaction amount.
These are two different things.
In a "blockchain" with a centralized validator set, there's no constraint forcing transactions to be public. The network will keep running even if the validators decide to stop publishing transactions. It's very much still a social contract.
Tampering (adding false transactions) is the only thing that could be hampered thanks to the requirement of client signatures: transaction/partial information censoring will still be possible. But in reality such a system will have the design constraint that funds must be seizable by the government, which in turn negates the only remaining technical advantage of a "centralized blockchain".
All that's left is the now empty word "blockchain". It's going to fit perfectly next to "democracy".
https://upload.wikimedia.org/wikipedia/commons/0/09/Redacted...
with citizens unable to discern between abusive and reasonable interventions.