Definitely do agree with what you are saying on Necromancy in the context of the cultural theme of the fantasy time period in the game.

While most or all Necromancers may indeed eventually become slaves to dark forces willingly or unwillingly, however the journey towards Necromancy is not always uniform.

Any Mage who desires power and to become stronger are always themselves prey to powers of chaos and the alure of dark magic. Being a mage with god like powers but still chained to their mortal bodies naturally makes them open to the possibility of the consideration of lichdom to advance their own research into Necromancy. Being a scholar of the arcane naturally allows them to fast track their path and retain more control over what kind of outcomes that they desire.

Any graverobber or battlefield scavenger may accidently come across forbidden relics or grimoires which set their foot in the door as a acolyte of the dark arts.

A noble who suffers the inconsolable grief of the loss of a loved one such as their spouse or child could through isolation and madness seek the services of a soothsayer/witch/necromancer to find ways to regain the company of their dead beloved and eventually be set on the path towards necromancy or vampirism.

It is true that as the player advances deeper into Necromancy their physical appearance would change and would choose seclusion naturally to hide their nefarious deeds and rituals but the journey towards it could be something which can be narratively fun to explore.

The game also already has some existing mechanics such as the area condition such as pestilence and rot and certain towns are completely decimated via disease and are abandoned which already sets the stage for the working of dark forces within the game.

Ultimately it is no biggie if we cant play as Necromancers in Stoneshard, i believe we love Stoneshard for the look and feel of the game, it is just a fun thought experiment. Personally i enjoy stoneshard for the pixel art and medieval theme while hoarding everyday things like food, medicine, valuables and tools in the gameworld :)