When writing fantasy or science fiction you have to create so much, this includes a lot of words. The names of people, worlds, magic or invented sciences and sometimes even more.
As a reader it can be very confusing picking up a book for the first time and finding it full of nonsense words. Some authors create new words for everything, days of the week, units of measurement, seasons and even social classes. It can be a bit overwhelming at first. So where do you draw the line at what to rename?
This is one of the problems I faced as a writer. I wanted to rename enough to make it feel like a unique alien world, yet not confuse my readers. In the end I decided to keep my renaming to a minimum, partly for my own sanity, but mostly because my book is more geared towards young adults and I wanted it to be as accessible as possible.
I feel the need to also defend authors who chose to do the opposite. One of my favorite authors, LE Modesitte Jr, always renames absolutely everything. It hasn’t prevented me from enjoying his work, though it did take me a bit of perseverance to get into it in the first place.