"In this work, we solve this problem by reformulating the construction to exclusively use cards with mandatory effects."
So it's more a of a subset of MTG's rules. Still, there are commercial video games out beyond MTG and they've been out for some time. Why has the game theory field not kept up with them?
Why assume that it hasn't? The paper cites http://drops.dagstuhl.de/opus/volltexte/2018/8805/pdf/LIPIcs... which claims to "show the undecidability of whether a team has a forced win in a number of well known videogames including: Team Fortress 2, Super Smash Brothers: Brawl, and Mario Kart."
Unlike previous attempts, which used cards that leave some room for Player agenda, this new version doesn't.