A cryptocurrency is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets.
But.. their biggest disadvantages are:
1. They are difficult to be understood and used by everyday people.
2. They consume massive amounts of energy to be mined.
3. They require expensive and specialized equipment to be mined.
4. Most of them are not scalable. It takes hours or even days for a transaction to be confirmed and it gets worse as more people use them.
5. Most cryptos provide anonymity and give a false sense of privacy, but if somebody ties you to your address they instantly know all the transactions you have ever made.
6. If you lose your key or if somebody hacks your account, nobody will be there to help. You lose all your funds.