I think there's something to be said about completing some games on yard difficulties, and Fire Emblem falls in that category. The category is puzzle games that require insane tactical strategy.

A lot of unit based RPG's function this way, and they do a really good job a lot of the time. But that is just one way to play the game, and quite frankly grinding through levels to "properly" beat a certain difficulty is certainly a better option for the majority of players.

There is something unique about finally completing a damning level, but it's only something that is there if the player has the drive to get that fulfillment.

I wouldn't say you have big dum, more likely you just value your time and the engagement of the game is more rewarding on lower difficulty, due to the element that is driving you to play the game. That is to say, it's aspects of the gameplay and the story that keeps you coming back, not necessarily the insane strategic plays needed to beat a hard level.

Both are completely valid forms of gameplay, the hardest difficulty is often min-maxxed and tends to account for a small section of players, and is probably included partly for replayability.