Failed iPad even before two year cellular contract has ended

I bought an iPad Air Two less than two years ago. I went to the iStore yesterday to be told that this iPad battery is dead and cannot be replaced - the iPad is therefore redundant. I find this very disappointing considering Apple is supposed to sell premium reliable products at a premium price with a reasonable life span. My cellular contract has not even ended yet, but the product has failed!

I bought an iPad Air 4 years ago and it is still working fine.

This redundant product is a great disappointment and I believe that I should be compensated for the failed product. Please advise accordingly.