As for the decentralization aspect: I think a lot of people in countries outside of the US would disagree with you that trust is not a problem with the banking system. Not everyone out there can just get a credit card with 2% cashback that's backed by the rule of law I enjoy in the US.
I think you've also sidestepped the issue of inflation. Just because the American public hasn't yet learned that their money's value is being printed away doesn't mean that they're not going to be the ones feeling the hurt in 5-20 years, particularly if UBI et al don't keep pace with their decrease in purchasing power.
I saw another one of your comments allude to the idea that democracy is a solution to this, but I don't ascribe to the idea that we should shirk technology solutions because political ones might exist. In many cases, technological innovation drives demand for political action. I don't want to debate the merits of Uber as a company, but I think it's hard to ignore the idea that the introduction of car-hailing apps created demand for governments to completely rethink taxi monopolies.
Ultimately, I'm not trying to make a case for Bitcoin. I'm trying to make a case for the idea that the adoption of and furor around Bitcoin is going to significantly influence the vNext of our banking system, even if that just means e.g. that the near-instant clearing of large Bitcoin transactions is showing folks that ACH is garbage, or that T+1 stock settlement is achievable.