IMO not possible to live without banks in next 20 years, or even more.

But i am pretty sure that crypto market cap will raise, and ratio between crypto/fiat cap will get smaller year by year in pure USD value. Currently it is around 500B-600B for all 5000 crypto coins, comparing to 91T in fiat. That is little over 0.55%.  Tomas Frey predicted that crypto will get to 25% by year of 2030. We will see.

In the mean time, we can enjoy high interest in crypto and convert earnings to fiat in amounts we need for personal spending.

Plenty of good services for this, which are already acting like small crypto banks (celsius.network , blockfi.com, apyharvest.com , crypto.com, nexo.io)

They all offer crypto interest accounts, and crypto borrowing (with crypto collateral)

crypto.com offer atm cards (have one - all OK)

apyharvest.com offer crypto retirement plans, crypto joint savings plans and crypto child education plans

Celsius.network have already 3.3 billion AUM (assets under management)

However, they are all centralized, like fiat banks, cannot open account without KYC to prevent AML. And you do not have your keys, so risk exist no meter how much all 5 of them are legitimate.

I personally use crypto.com because of their crypto atm card, but i keep there only enough coins needed for having card. I would never place 100% of all my portfolio on any of them, no meter how big their interests are.