It’s a matter of adjusting the long-term funding conditions, notably (but not only) in the so-called periphery countries which are in most need of this support. If QE fails, you won’t have any more ammunition. Throughout the crisis, the ECB has devised efficient instruments to face up to new situations, while remaining within the framework of its mandate.
It makes it more difficult to explain to customers why their application for credit was unsuccessful. The risk of unfair discrimination against individuals or categories of customers must be dealt with, also in view of forthcoming regulatory interventions regarding artificial intelligence. These difficulties do not only affect banks, but apply to anyone who uses similar techniques to grant credit.