Quite the opposite. Using blockchain for anything but timestamping is worthless, because there are faster and less resource-intensive protocols for about everything. Data storage, for instance, has distributed hash table, and change coordination has leader election or consensus protocols.
> Bitcoin, Ethereum and others don't use a blockchain just for timestamping either, but store all sorts of data in it (transactions in Bitcoin and even complete programs in Ethereum).
You're putting the cart before the horse. These "all sorts of data" in blockchain are in fact documents that get timestamped -- the timestamp says "document X was issued before document Y". A Bitcoin transaction in isolation from all the other transactions is nothing more than a semi-random string of bytes. For it to be a money-like thing you need to have previous transactions (and how do you know they're previous? by timestamp) that testify the account had enough resources for all the output.