If you haven't played a game like this, there is a learning curve. I've been playing stuff like this for decades and there's still lots to explore, in purely mechanical terms, with BG3.

That said, it is very much worth the initial investment. I found playing Divinity 2: original sin very much prepared me for BG3. You could start there a little more cheaply before delving into this expensive title. At least then you can see if you enjoy this style of game.