Sparky is the Arena AI, but no one ever accused it of being a good Arena AI - it is very much only there for the new player experience of playing against a dumb computer when you're first exposed to the game and don't know the rules, or for the computer equivalent of "playing against a goldfish" a deck you made to see how it draws or combos. It's not a Chess CPU.
I hope I also did not accuse it of being good, but the observation I was trying to make is that -- according to the article, I have not myself confirmed the claim -- they run the card evaluation logic and gameplanning locally, not in a data center full of H100s, which I consider to be quite a feat given the free-text-y self-modifying rules of M:TG
One of the big things to note is that Sparky plays very basic decks, with few complicated cards and combos. Rules-based AI could definitely play at a basic level using a beatdown strategy, but give it some sort of control/combo deck and it would struggle.
Hearthstone allegedly had bots hit Legend rank back in 2014 playing Aggro Shaman. Those were believed to be pretty simple rules bots, so yeah +1 that approach gets you pretty far if you have decks crafted for it.
