I'm pretty new to D&D as a whole and a new DM who's running Lost Mines of Phandelver for some friends who wanted to roll their own characters. As a result, some of the magic items detailed within the mines don't really seem exciting for my current party and I'm trying to make some replacements to make finding them a bit more fun.
One idea I had was to leave my party's monk a scroll from an old master monk that would grant some ability upon being read (in-world kind of shown as the teachings of that master on the first steps to enlightenment). This idea mostly came from the flavor of monks caring little for material wealth (and thus likely not being interested in a general +1 monk weapon, but rather being interested in beginning a journey of enlightenment. However, when trying to either find an item whose effect kind of worked for that (Referencing the Player's Manual and Lost Mines Book as a starting point), I found that items that just impart knowledge/training/improvements to class abilities seem exceedingly rare in D&D 5e. Are items like these avoided for balance reasons or more for the general flavor of "magic items"?
I'm hoping to create an item with similar power level to Hew/Lightbringer which are +1 uncommon weapons with conditional side effects against specific enemy types. However, I also want to make sure that I don't make something inherently broken in the format of D&D which will make planning any future encounters for this character significantly harder (or just make them far stronger than they should be). I'm fine with this item in question not necessary just resulting in a raw bonus to damage dealing potential and being focused on other traits instead (The skill being granted having some combat potential does feel consistent with the items it will be replacing, even if that bonus ends up being something such as a bonus to movement or empowering Ki usage in some way rather than the raw boost normal magical items have)
In summary, are items that just grant skills (whether these skills be proficiencies, or combat boosting effects) by being consumed/read generally seen as something to be avoided in D&D? If these types of items generally aren't aimed at being avoided, what are some reference items that could be pointed out to understand how to scale these items appropriately and roughly match the power level of various rarities of items? If items that permanently teach PCs new abilities are generally avoided, what are some good alternatives to model a system for a PC beginning a journey of learning/spiritual enlightenment in an item?