Ok so basically blockchain is used only for cryptocurrency and that’s it. For anything else it’s useless because everything else can be created with existing tech
You can create cryptocurrencies without using blockchain technology too. Same applies to everything else. What is blockchain? In simple words, a method of maintaining database where data is stored in blocks and hash of each block links to the next block, that's it! You can adopt this principle and apply blockchain for maintaining database for any project. It will neither make your website decentralized, nor tamper-proof unless you take care other stuffs as well.
When I talk about other stuffs, it includes the methodology of creating new blocks, place of keeping database and difficulty of tampering database.
Methodology of creating new blocks : If new blocks are added to blockchain on sole discretion of creator then your blockchain is not decentralized and adding no value. You can simply go forward and design your project with simpler database structure. If, there is some protocol of adding new blocks like in case of Bitcoin we have the protocol of adding new block when someone finds a hash whose value is less than the target difficulty, only then your blockchain is decentralized and adding value.
Place of keeping database : Next important thing is that where are you keeping the records of all blocks. Are these kept on single device or spread across number of devices where each device is keeping the copy of blockchain. If the storage is centralized then your blockchain can't be said decentralized and adding no value. On the other hand, if anyone can maintain the copy of database on his system then it would be difficult to temper data across all devices making your blockchain valuable.
Difficulty of tampering database : This is most important point. If you can manipulate the data that is stored in blockchain and re-write whole blockchain easily, then your blockchain is not decentralized and adding no value. The value of blockchain depends upon how difficult and costly is to manipulate the data in any block and re-hash the blocks above that. In case of Bitcoin, even manipulating one block less than the current height and mining two blocks above that to make that the longest valid chain is
very very difficult which makes bitcoin decentralized up to great extent.
So here is your answer. You can use blockchain technology in any stuff you want no matter if it's cryptocurrency or a social media site. But if your blockchain is not fulfilling these three points then it's better you adopt simpler structure of database maintenance. On the other side, if your blockchain fulfills these three points then you can surely create any project no matter if its social media site or any kind of other utility.