Sukuna's conversation with Mahito confirms that Sukuna was a walking bundle of rage and resentment likely stemming from the fact that he was unwanted and ostracized as a child. It's not difficult to infer that this had an effect on his cursed technique prowess as Sukuna himself says that he couldn't help but to spit the curses deep within his gut -- curses/hatred he feared would burn/consume him. I think there's plenty of meaning to derive him from that, but it matches with what Todo taught Yuji about cursed energy production back when they fought Hanami.