The spell levels inherent to the items are always so low that they are essentially worthless. I can cast a firebolt 40 times designed for use by a level 3 character. Why is this even a thing? Same with 99% of all of the items with any sort of spell cast associated with the item. They do nothing. Amp damage, Teleport and Decrepify are the exceptions because they work differently. Maybe oak sage, but it can’t stay alive because it’s so low level. So it’s a dead affix. We cast >lvl 45 spells. What use is a level 1-5 spell?
It’s a nice idea, and in Diablo 1, scrolls could be top tier items utilizing the same mechanic, but in Diablo 2, cast charges and cast on x spells have been entirely lackluster in every regard.