Interesting, but decentralization does not equal privacy. Indeed, it might make privacy worse by sharing the data more widely and making it even easier to get copies of the data. Consider, for example, BitTorrent, which has a pretty decentralized distribution protocol that also makes it easier for third parties like the MPAA to observe who is sending and receiving the files.
Even using a privacy-enhanced blockchain isn't necessarily sufficient. Blockchains do not provide anonymous messaging. Therefore, a recipient R of a transaction can identify the sender S if R can observe S sending the transaction. Yes, this problem affects Bolt, Zcash, Monero, etc.
That's basically using a proxy, and so it has the same security. If the proxy is/geos bad (say, your VPS provider reveals your IP to some interested guys with guns), then you lose (anonymity). If your proxy remains good, then all that can be learned is the transactions originated at the proxy. However, the proxy does serve as a potential pseudonym, and so if the collection of transactions reveals something identifying, even if any one transaction doesn't, then you lose.
Even using a privacy-enhanced blockchain isn't necessarily sufficient. Blockchains do not provide anonymous messaging. Therefore, a recipient R of a transaction can identify the sender S if R can observe S sending the transaction. Yes, this problem affects Bolt, Zcash, Monero, etc.