Yeah but you need all three cards in your hand to be effective, this, apophis, and a high level dinosaur. Big evolution pill is better because need a dino instead of reptile, which is majority of your deck anyway.
I recently got Rex and haven't used him in the meta yet (I don't have a good dino deck yet) but it is a pretty good card. If you are lucky enough, you can summon a card like Megazowler or Sword Arm of Dragon on your first turn.
The evaluation says not useful. Maybe not the most efficient way to build your deck but by tossing a single copy in ur deck this could turn the board around on one turn. Possibly win the match in which case i say its def useful. Just like order to charge is using 2 cards to kill one. This is similar because u can summon a reptile and activate this card to summon a 5-8* maybe higher dino card to board swing for the win. Granted right now megazowler is the highest non fusion dino and its attack is only 1800 but becomes 2100 with dino kingdom. New cards will make this more valuable but for now i guess ive talked myself into not SO useful right NOW lol. What a waste of time i just spent writing this, sigh