I'm in banking at a startup level and I'd have to disagree with this.
There is tremendous fear in the industry right now over being seen as outdated or dinosaur, especially with all the blockchain hype.
You can make simple technology choices like moving from a stateful SQL database over to a blockchain ledger like Sequence, and in doing so, you will attract a way higher calibre level of talent. You will also have way more people interested in working for you, and the skillsets and knowledge learned within the company for doing it will future proof you far better than going the boring old route.
I'm one of the contractors that rolled out instant transactions at CBA.
The feature is absolutely hype, and a selling point, or was til the RBA required everyone else to follow suit.
But it doesn't change the fact that fundamental things that cannot be allowed to fail should not be built on twigs.
CBA worked with Wells-Fargo to build a blockchain ledger, running atop skuchain, which itself Go and JS. That's a lot of hype and new in one place.
But it wasn't in a simple systems-critical place, it was done for one contract, with one customer first, with regulatory approval for the experiment, to see if blockchain technology was feasible. It was also not proof that this can scale, that needs more experimentation.
Lots of simple things are fundamental, and you do not mess with those.
Simple/complex isn't enough to say whether you should experiment, because experiments should be as far from impacting your bottomline as possible.
R&D should stay in R&D, until it is proven stable. You can't afford to build a house of cards.
But if you reach for that new language that hasn't been battle-tested yet, you're probably screwing the bank over.