I've kept my 5th gen on 14.8.1 (last version of 14) for performance reasons as hinted above. But based on the positive experience of the last post, will now likely upgrade to 16.
As a note to my earlier post, apps no longer in the App Store now are kept and continue to work after upgrade. But strangely, when only doing a restore without upgrade the app no longer functions since the App Store app refresh failed.