In my opinion, the main weakness of Bitcoin is the limited internet service. because bitcoin can only be accessed using the internet network. and we all know only developed countries where almost all of the population can access the internet. whereas in third countries only 50% of the population has access to the internet. but I am optimistic that over time the internet network will expand. and bitcoin will be a revolutionary currency that is very suitable for us to use in a digital era like this.
There's this hardware wallet such as Ledger Nano S/X, wherein a user would be able to receive funds even without the use of Internet. But things are different when you will send funds to another wallet, if I'm not wrong. So maybe, from this, there is still a chance in the future to solve this, if this will really be problem in the future.
The biggest disadvantage I think, but also one of its advantages is its volatile market value. It is a downside on the aspect of it, being a digital currency because not all people are interested to invest because there are risks of losing money. Advantage on the other hand for investors because it gives profit.