Its an incredible card to turn the late game on its head, protect you from a lethal strike, and likely leave you with the board presence to win on your turn
Its second attack is good against decks that take some time to set up, as it can easily knock out opposing basic Pokmon, making it a reliable alternate attacker in Raging Bolt ex decks
I want to reemphasize that these cards are usually being sent from individuals , not full storefronts, so theres less security when it comes to judging card conditions, returns, etc
Decks that blink or bounce Sundering Titan can utilize its effect repeatedly, leading to an environment where its nearly impossible for opponents to keep basic lands in play
This isn't the only thing that determines value, but the most important
I love that interested self-targeting but only for your activations of things there - like Equipment