I think one of the main flaws is how confusing the game is, it seems like a lot of people are having that issue 😅 The downsides of not having any playtesting.
To cast spells, you hold right click, then draw the symbol for the rune you want to cast on the page that appears, and release right click to cast it! (The confusion may have been caused by the UI not scaling properly and parts of it missing, again our fault haha)