There is another post with the same issue here: Turkish Localization Error (Capital “I” Letter) - Bug Reports - Last Epoch Forums But since it has been closed, I had to create this post stating the same issue.
Screenshot: Imgur: The magic of the Internet
Above sample shows that even on the main menu there are lots of font failures. There are even much more in-game.
As I am a player who gives strong importance to visual consistency, this issue really drives me to refund the game.