Like people have been saying, complex is not necessary but variety is and sentence structure is. You don't want to be constantly repeating the same few words but you also don't want your regular characters speaking like a linguist.
Yeah. Once I wrote a whole bunch of stuff that I though was really cool but then I switched to a different book and realised that I just wrote your typical evil family so I completely changed the family into morally grey and into a way that let me still break off my MC from them but also made...
My sister the villainess is a great book as there is plenty of humor and a good plot sewing through the jokes. There is a troll chapter within the book though where the author makes the MC act like an idiot from the princesses POV but it is completely explained in the next chapter.