The Air 5 is literally the latest model...
I will never update this Xʀ. If Apple forces me, I'll throw it into the bonfire myself.
iOS updates severely impact performance and obliterate battery life. I'd like a perfectly functioning device for a very long time, if possible. And it is possible! Never update and it will work correctly forever.
Like I said, the mere suggestion that because a device isn't updated it becomes completely useless and should be thrown away (!) is ridiculous.
A final clarifying paragraph: on the conspiracy theory thing, I don't know whether Apple does it on purpose or not, but frankly, it doesn't matter.
I mean that I don't know whether they could do more to alleviate issues or not. New features consume more battery and put more strain on the processor, which consumes more battery. Whether Apple can slightly alleviate the impact of that, I don't know. I'm inclined to side with Apple here, even: it's more possible that they optimise it the best they can than the opposite, but it doesn't matter. The end result is far worse than I'd like. So yeah, even though I'm more inclined to side with "there is nothing nefarious on purpose going on", it doesn't mean the impact isn't there. No conspiracy whatsoever.
What matters is the final result: Apple obliterates performance and battery life through updates, and I can do nothing to prevent that other than never update anything, regardless of whether it's the latest model (My Air 5 is the latest model and will remain on iPadOS 15), or an older device (my iPhone 6s is not supported anymore and will remain on iOS 10).