True. But also, another thing, in my own opinion, that limits Bitcoin's ability to replace the dollar or any fiat currency, is scalability and fungibility. Especially scalability, as Bitcoin won't be able to handle all of the world's transactions without a proper scalable solution, in which nodes may need a huge amount of resources like storage, to be able to store the ever growing blockchain database.
Nevertheless, I think that Bitcoin works fine alongside fiat currencies, instead of becoming a main currency itself, reducing the massive blockchain bloat that it would have if used by everyone in the world. Just sharing my thoughts.
If Bitcoin would be the main currency of the world, imagine how many daily and simutaneously transactions we would have.
The fees would be much higher or we could never complete our transactions. Bitcoin doesn't have capacity yet to be the main currency, some upgrades and updates are needed yet... Scalability is the problem and I agree with you.
Fees might not be the main concern then
It seems that the whole paradigm of a centralized blockchain should be replaced with something more scalable and robust, since right now every transaction gets propagated endless number of times through network because each node should keep an up-to-date version of the blockchain. This may be completely unfeasible to support once Bitcoin gets past a certain point in adoption across the world unless a totally different approach to confirming transactions is applied
All quoted above are true.Bitcoin is now getting more stable than it is before, the adaption of the users are increasing in number and transactions and features were happening in an instant. But still it is not yet absorbed or even heard by atleast half of the worlds population so it will never be imagined that in 15years it will be the universal currency.