I just have a line of questioning to offer.
If you want to see all the story content you don’t even have to play past Normal Mode. Is that your goal?
If you want to see all the weapon types you will have to make it to level 61. Is your goal to hunt all the loot?
Do you want to see all the skills your character can use at once, and fight all the enemies in the game? If so that requires reaching level 72 and then unlocking OP levels far enough that OMG WTH is accessible.
So that being said, your level attainment required really comes down to your curiosity about game content.