Let's talk about flexibility.
This instant spell combines two of the most powerful effects in MtG: card draw and counterspell. Of course, you can't use both sides, but that's where flexibility comes in — you use it according to your situation.
The first effect also plays around Narset's draw block ability, which is a big deal in Pioneer. This means that Blue-White Control decks may want to play Thassa's Intervention instead of the more typical Hieroglyphic Illumination.
The second effect is just as good and even stronger than most similar counterspells in the format. So it's a definite winner!