Unlocking mementos/leveling characters feels awfully grindy and out of theme.

Why do I have to build wonders to level up a military civ. Why do I have to go to war with a civ focused on diplomacy and culture. Why do I have to do these 3 times EACH just to unlock the memento I want. At this point I'm burned out. They really should reduce the amount of challenges for each leader and also maybe tie in difficulty instead of repeatability of challenges.

Maybe something like doing it on easy/medium/hard instead of 3 times and doing it on immortal/deity should give you all 3 challenges at once.