tbf: Blackjack could be a fair battle system in an RPG - a blackjack is a critical hit, but other than that your damage scales with your result, but busting is a miss. Enemies could have scripted patterns like a humble worm always starts with a 3 card and never hits (so their max result is 14) and there could be an assassin that always starts with an Ace and the strategy is to Insurance Counter.
^That seems to follow the SNES trend of trying to look way too realistic for what the SNES is capable of and looking bad now because of it
Have you tried Dungeons & Degenerate Gamblers? It's very similar to that concept