For me, I think the major disadvantages are just in terms of the market being a volatile one by means of price fluctuations, the rapid drops at any point in time. It could be influenced by almost any world happening at the time I think resulting in great or small losses. How about the high level of unpredictability? That should be considered too.
And for another major disadvantage which is the security risks. The hacks of transactions, wallets, the high level of fraudulent activities in the Bitcoin world. Also imagine you misplace your private keys or security phrase to a wallet while transferring wallets, I guess it's all gone. An example, the man looking for his hard disks in the dump.  These are major lookouts while investing.