They get away with the copy-paste because the combat system is fundamentally extremely solid.
The good thing about this is that programming-savvy fans have been creating free fan-games based on the formula for the last decade or so. As with any fan-made content the quality is extremely variable, but I have found some of the newer releases to be genuinely good games, better than anything GameFreak has put out in the last 20 years. Pokémon Unbound is a personal favorite - if you enjoy the fundamentals of the Pokémon games but feel the lack of creativity and puzzle-solving in the official releases I would suggest giving them a look.
Slay the Spire has a decent iOS port