That is not true!
Mass adoption has nothing to do with banks!Not even in the slightest!
Please explain me why people should use a wallet where probably the bank will have the control of your bitcoin funds when they all could use wallets in which they will have the total control of?
What you explain already exists today? Or what do you think Coinbase is? They act like a shitty bank!
Bitcoin will grow and evolve completely independent from the banking sector.The same will happen with other fintechs!
Your last sentence has to do with ease of use, meaning progress in the technology and user interfaces, and not with any incumbent institutions!
I'm saying that banks will inevitably convert to Bitcoin (the same way camera making companies converted from analog to digital photography) and will offer services that would greatly simplify the use of Bitcoin for the average person. They will go at the supermarket and will pay in the same way they have always done their whole life. We need to accept the fact the average user will never download a Bitcoin client and setup their own envinroment, simply because they have no knowledge or will to do so.