Thanks for the thoughtful reply, I'll respond to each paragraph:

1) Not to any particular part of the world, to most people generally. It's simple to see that this true, if you have money, you keep it in a safe place only you have access to or in a bank, not with your brother. I think this was true even in the days of gold and silver.

2) The main downside is that the custodians might collude and run away with your money.  The other downsides are the politics involved in chosing the custodians, the day to day annoyances of running the mint (even if the software is great there will always be tech issues that will have to be dealt with), the politics of chosing a fair fee structure to compensate the custodians, etc.  In addition, having your friends and family serve as custodians might be better in terms of decentralization but it also introduces drama into relationships that you wpuldn't otherwise have. 

3) It could be any "coin", the point is that it is a mistake to think thay Bitcoin is invincible. Ethereum has a lot of network effect and if they get a scaling solution with less downsides it might be preferred by the billions of people that will need to be onboarded in the coming decades. More worringly, cbdc-esque "coins" will come with the threat of state violence to reinforce their network effect, of course they have their own downsides (lol) but the fewer downsides our scaling solutions have the better.