The biggest disadvantages from bitcoin in my opinion is still vulnerable hack and bitcoin is always used for the negative activities. That is seems to me that the weakness of bitcoin makes someone difficult to believe with bitcoin.
That is one of the things that could prevent bitcoin to be accepted as payment. In addition, many scam it will affect my opinion. If bitcoin can be overcome, I believe bitcoin will be accepted as payment.
When you deql with bitcoin you just have to know that there are risks anyway.
As per my understanding, whatever is there in this life there will be advantages and disadvantages of everything, likewise bitcoin also has disadvantages like price fluctuation, not common among the public because people don't trust so easily as people think it is a scam which is not the case because it is decentralized and the value can change at anytime so most the people don't trust for that reason.