All the discussions itt aside, I agree when it comes to mainline games/traditional hacks that more or less strive to emulate them. But Server 72 ([LT] Server 72 [COMPLETE]) shows that you can make an “FE” game that’s balanced around casual mode, it fundamentally wouldn’t work in Classic Mode and even in “forced casual mode” it’s one of the most challenging FE-likes I’ve played. Although it is arguable if it can even still be called “FE” when a lot of the systems are very different, otoh a lot of the systems are still classic FE, so I think its worth mentioning as a counter argument.
Also I guess a game definitely can’t be balanced around both, if a game is reasonably completeable in permadeath mode, casual mode IS akin to a cheat code that makes the game a lot easier.