I really disagree with this - product plans are pretty worthless when they come into contact with reality and customers, and businesses which don’t learn from their customers are doomed to fail.
The main driver of growth, recommendations and product-market-fit is listening carefully to customers, because their needs are varied and surprising and often don’t conform to the solutions they are forced to use. Often very small changes suggested by customers can have a big impact on how useful something is - things like ordering of lists, or filtering options.
By that I don’t mean listening to the most vocal ones or just reproducing what customers claim they want, but if 20 of your customers tell you the same thing is not as they expected, you’re probably wrong, and should adjust your plans to address what the customers want, not what you thought they might want before you exposed the product to users.
Monzo still has a way to go on that front as well, but it appears Starling have not learned that lesson at all and if anything are doubling down on their greatest weakness - their refusal to listen to customers.