Interesting theory.. I'm a relative newcomer to Defi having got bounced rather violently back in August when my account was looking quite healthy..
However, one thing that I'm seeing is that it is already possible to hold your funds in gold backed tokens which you can spend, invest or withdraw for physical gold at any time..
You can also hold 'fiat based' tokens that match the USD, GBP, EUR etc as well as the high cap tokens that are currently flying through the roof. Then you have the microchips, high risk high return tokens that become the next 'big thing'. As to whether they stay the next big thing, that's another matter.
You can use your holdings as collateral for loans, credit etc, earn much higher rates of interest on holdings.. Pretty much everything you can currently do with a bank account. You can even loan yourself money to invest in high interest tokens and use the interest to pay back the loan.. Then you can reinvest that larger amount again..
You can also send funds to other people in an instant, cheaply and in large amounts in other countries (this is what Ripple was being used for) without any questions asked.
Used correctly, it can give you absolute control of your money without the risk of some 'authority' raiding your account for an unpaid tax bill or fine etc. And this is probably was Ripple was recently raided because the authorities don't want you to have such freedom and control over your own money.
The only downside at this current moment in time is that the majority of DeFi is operated on the Ethereum blockchain which can be very expensive to use. This is down to network congestion. However, Ethereum 2.0 is supposed to correct this plus there are many other blockchains being developed that could end up rivalling Ethereum..
It's a rapidly changing environment and something that only a tiny percentage of people use so the growth is going to be massive..