Seems apple have stopped allowing me to access apps on my ipad mini

You are perhaps misattributing blame here; it is Amazon (not Apple), that has dropped support for all versions of iOS preceding iOS/iPadOS13.

The first generation iPad Air, iPad mini2 and mini3 can only be updated to iOS 12.5.5. These and other early models of iPad lack the necessary hardware (specifically RAM and CPU) to run later versions of iOS.

Some App developers have dropped support for iOS versions preceding iOS 13.x for technical reasons (often because APIs or software libraries upon which they rely have been updated in the new version of iPadOS, making their App incompatible with earlier versions). 

Whilst many App titles remain compatible with your iPad, if you want or need to access to Apps requiring the most recent versions of iOS, you’ll need to consider replacement of your iPad with a newer or current model that supports iPadOS15.

Sorry, I appreciate that this may not be what you were hoping to learn.

I hope this information provides clarity as to your available options - and the fundamental limitations of your iPad.

While your iPad may not support the AmazonApp, you can still access Amazon using a regular web-browser - be it Safari, Firefox or other.