

You’re specifically paying for an agreed upon amount of time with the product. The negotiated price reflects this limited access to the product.
‘Licensing’ something with no stated time frame that one side can arbitrarily choose to end at any time makes little sense and they know it. They were perfectly happy with leveraging the assumption that you owned a copy of the product up until it became inconvenient to them.
It’s still possible, but only with a physical Kindle device and I believe only one of the older ones. You can copy files off those devices to your PC and crack them that way.
Otherwise I’m not aware of any other method. It really sucks too as my favorite genre literally only exists in the Amazon ecosystem (small indie authors that rely on KU and so don’t publish anywhere else)