Basically, banks force apps or users to require you fully revalidate user consent every 90 days. And it's quite an annoying process. That means any app or integration you want to build, requires 10 minutes of your time every 90 days or they stop working. It's killed many Fintech's.
It all works on paper, but is drafted into law by politicians who have no clue about technical challenges and user experience. So in the end, it works exactly as designed by the banks: it doesn't