"Well you still have to pay the mana cost, and it's instant spells only, how bad can it be?" It means you can draw lots of cards with Brainstorm, blink Chun-Li to get her out of harm's way with an Ephemerate, or make your board untouchable with a Teferi's Protection every turn
That effect normally isnt that impressive, mostly because you would go down a card for tempo alone, but because you have the Coven to play later, that isnt true in this case
Its infamous powerful effects and level 3 status will deliver good performance at tournaments
Starbirth allows you to search your deck for any two cards and add them to your hand, fetching vital resources during your turn
Your clues can be sacrificed to their own effect, or to enable a card like Deadly Dispute, either way your Tireless Tracker will be gaining some counters
This means you can draw as many cards as you like, but you lose one life each time