I have an iPad whose hardware has life left in it, but as time goes on it's more and more it's worrisome to run a connected device without security updates.
My partner’s mother has an old iPad mini from the same year and it’s perfect for FaceTime calls. It’s basically an iPad 2 SoC.
I wouldn’t do any personal banking on it however.
At least my iPad Air 2 from 2014 is still getting updates.
I recently brought a used SE (1st gen), as a low-end test (running iOS 14).
I also purchased a used iPhone 8Plus.
As soon as your hardware stops getting the next iPadOS version (for iPads this is like 6+ years after release), the clock starts ticking and you have perhaps a year while you can still trade it in for a meaningful value.