I purchased an IpT5 when it first came out, and STILL have it to this day! However, I stopped using it mainstream around 3 years ago. What changed was I got a used iPad Air (the 2013 model, not to be confused with the ones that came out a mere few years ago). My IpT5 was on ios7, while my Ipad Air was on ios8. Both never got updated. That made it worse for the apps getting updates, but I do still use apps that never got updated for 64-bit support.
Issues of me never getting newer versions of iOS, the IpT5 is indeed maxed out at ios9.3.5. It's also long in the tooth as far as specs go. It can still run, but the range is "OK" to noticeable sluggishness. I first got the IpT3, then IpT4 as well due to improvements to the screen, but the IpT6 and IpT7 never offered those.
$300 for a 128 GB isn't too bad, but at that price, I may as well shell out another $130 for the basic, 8th gen Ipad. But even then, I'm having a hard time justifying that (that price range also has to compete with the Nintendo Switch), so I've been in limbo for the past few years about a replacement device. Old me appreciated the portability of the IpT5... fits easily in your pocket! But these days, having a larger screen suits me better.