Not to mention the massive difference in age between BG3 and OSRS/RS3. RuneScape’s running on an engine that was never built with more than 2 body types in mind. Changing that is probably a much more monumental task than OP realizes, the armor models being just one (big) roadblock.
I’m no Jagex defender but I feel like the fact that they added even this small change to a 23 year old game’s character creator shouldn’t be labeled lazy. All that will do is discourage developers from trying.