Bungie can adjust the grind but they can't fix stupid.... sorry hun you're screwed.
Its a videogame, its casual by definition, hardcore is getting off those lard deposits you call a butt and climbing a mountain for example.
Playing a videogame = remotely hardcore? lol what a muppet.
except every activity in life has a hardcore and casual version.
Take working out for example. lift a couple dumbbells and take a walk. That's a fairly casual workout.
Hitting the gym, doing a full blown workout pushing your limit on each machine there, that's a more hardcore workout.
a gaming comparison would be playing a game that is used in the competitive scene. So let's look at CSGO.
You could just play socially, only playing when friends are up for a game or two, or just playing a few games on your own for the fun of it. That's casual gameplay. you may or may not put some effort into learning specific game mechanics. Maybe you have a good idea of the bullet spray patterns of a few guns, and know a couple tactics for some maps.
Then there's the competitive side that is much more hardcore than that. Knowing points on the maps to bounce grenades off, knowing spray patterns for every gun, knowing tactics and counter-tactics for each map, taking care of your weapon economy...
Gaming in itself may not be as physically demanding as climbing Mt Everest, but in saying that climbing a mountain is hardly mentally taxing. You're just putting one foot ahead of the other. That's a pretty mindless task giving you time to think about literally anything else. Hardly any precision dexterity involved in walking.