For me, the biggest dksadvantage of bitcoin is; it is not widely accepted. Infact, some countries are banned this kind of technology. If you want the list here
https://en.m.wikipedia.org/wiki/Legality_of_bitcoin_by_country. Second, it has no physical form. You cannot spend it ti any physical stores. Only few stores are accepting bitcoin. You need to convert it to cash in able to buy. Third, bitcoin can be lost. Just like physical.money, it can be lost. For example. You have stored your btc at your pc, but the pc crashes. Your wallet is lost and also your btc.
i think still no country has banned bitcoin although they also have not yet turn it as legal also. but still people from all over the world are using bitcoin continuously. and hope that they will continue using bitcoin for ever.