The list of supported devices is impressive. The iPad Air 2 came out in 2014. 12.9-inch iPad Pro 11-inch iPad Pro 10.5-inch iPad Pro 9.7-inch iPad Pro iPad (7th generation) iPad (6th generation) iPad (5th generation) iPad mini (5th generation) iPad mini 4 iPad Air (3rd generation) iPad Air 2
I'm still impressed by my iPad Air 2. I originally bought it for product demos/ as a presentation tool for work, but now use it regularly for personal use. My only regret is getting the 16GB version.
To this point, I wonder how much Apple is struggling with this "problem". There is very little value in upgrading to newer iPads. Even for those of us that have the disposable income to spend on them, we can use a 5 year old iPad which acts almost identically to the newer ones. Yes, Apple has pushed some of the power features that the newer ones can do, but for those of us that just use it for notetaking, internet browsing, social media consumption, etc there has been virtually no need to upgrade. The second hand market is saturated with perfectly good devices for $100-$150 that perform in ways that are nearly indistinguishable from brand new iPads for the 95% of the population that are using these devices for media consumption.
Sure if you use the iPad for media creation then you can benefit from a newer one. But for media consumption, the older iPads perform nearly indistinguishably from the new ones.