Of course when you quantize deck quality to such a degree I'd argue it's not fun anymore. YGO is already not fun anymore because of this rampant quantization and it didn't even take LLMs to arrive here.
In principle, LLMs could have a much higher strategy ceiling than deterministic decision-tree-style AIs. But my experience with mage-bench is that LLMs are probably not good enough to outperform even very basic decision-tree AIs today.
Worse, it’s difficult to tweak. For example, what if you want AIs that play at varying difficulties? Are you just gonna prompt the LLM “hey try to be kinda shitty at this but still somewhat good”?