One flaw I see is that you can’t hand someone your Bitcoin. It requires electricity, computer knowledge and availability, web access, and remembering your codes for both parties.
We use the above for our fiat dollars for convenience but it’s not REQUIRED. I can take my dollar to the store and buy a doughnut.
Another flaw is that fact that if I forget my code (get hit in the head, die, get dementia, whatever) that money is gone. With banks there is a process for retrieval.
Another flaw is that deliberate or accidental shutting of the World Wide Web, or electricity, renders you incapable of accessing your money. In limited ways this is true of fiat dollars too but it’s limited and there are means of retrieval.
Another flaw is the lack of accountability for the operators of Bitcoin. Banks are held accountable and yes I know not perfectly but in the main they stay in line. Tracy the teller will not successfully clean me out. Wells Fargo can’t just wipe my accounts clean with no relief for me.
Unless the government entirely collapses in which case we are all doomed.
My lawyer is the executor of my will - I have a "cold wallet" with my bitcoin holdings and that will be distributed after i pass away. No electrons needed. My kids are more tech savvy than I.
I can purchase a bunch of different crypto currencies with bitcoin and purchase just about anything with those.
My crypto holdings are NOT as investment speculations (as are my stocks). They are an insurance policy should we enter a hyperinflation cycle or if SHTF and the banks go tits up.