It gives the setting more consistency those are racial distinct features if one dislike such feature why chose that race in the first place? It is not like everything must look varied as humans. Otherwise what could stop me to make a white skinned Ghitianky that looks like Jhonny Depp?
It makes the setting more coherent and it create diversity among the race that contains. If everything would look the same what is the point to make a different race from the humans. Let's just make all humans.
Pretending a not Human race to have Human tracts is quite well... A pretense.
1) How does it affect your enjoyment of the game that other people are given more customisation options that you are not required to use?
2) Are you against the current customisation options that allow you to make characters with any combination of skin, hair and eye colour?
1) Yes it does. As i play forgotten realms in both pen and paper and videogames since i was a child. Adding things that breaks the lore smash the credibility and the immersion the setting provides to me. Is not a necessary add on. What needs to be done in my opinion is move the current elven head in the half race elf. And then implement proper elven head. In the case of OP i think wild elves would be perfect to her. Also again adding human diversity of a race that again "Is not supposed to be human at all" is completely unnecessary and kills off the distinct tracts of that specific rest.
2)No really. I even used that feature to create my tiefling as my tiefling is supposed to be one coming from a regular fiend and not an Archdemon or Archdevil wich is perfectly in the lore. However from custom color palette to having elves with the bone structure to reflect different HUMAN RACE etnicy there is a whole lot of difference.