My iPad Air A1474 won't update past iOS 16

The first generation iPad Air (A1474 - a.k.a. iPad Air1) cannot be updated beyond iOS 12.5.7. The iPad Air1 is too old to have any residual trade-in value.

By contrast, the second generation iPad Air (a.k.a. iPad Air2) is capable of update to iPadOS 15.8 - and still receives periodic security updates. The Air2 does not support iPadOS 16/17.

You can establish eligibility and an estimate of trade-in value for your iPad in your country/region here:

Apple Trade In - Apple

You can confirm your model number from iPad settings:

Settings > General > About

Not sure which iPad you have? Identify your iPad model.

You can trade in your old iPad Air, have a look at this Apple page:

Apple Trade In - Apple

As for keep on using it, depending on which apps you use, updating those app will require newer iOS versions, for example banking apps, social media apps, browsers...