"De-Fi" has its limitations since it's fairly new in the mainstream world. Blockchain is still unable to scale to millions or even billions of people worldwide, so the experience will not be the same as with Banks. Fortunately, scaling solutions are on the works with the hopes of putting an end to such issues. If all goes well, "De-Fi" might beat banks in the future.
Well, scalability is one of many important things that need to be addressed, but as you said it won't solely depend on it. Though fixing the scalability issue is one step forward, but defi needs more than that to truly compete with banks.
Its been in the cryptocurrencies spaces that blockchain and defi have become a buzzword. Like some people lured and became a maximalist that think cryptocurrencies will replace fiat, so does with defi that will replace banks. It's not the matter of bank
or defi, but defi
and bank will/could coexists with each other. Don't get me wrong though, cryptocurrencies give us the possibility we can't imagine, but the world needs to comply with the regulatory issue.