What? Mythic is a completely different game installed on your PC? It's just a higher difficulty with some extra mechanics, more hp, more dmg, more punishing. The 15 ilvl difference from hc reflects the difference in difficulty.
The harder part in mythic is to have 20 ppl all the time, each run and work together perfectly, because the mechanics are not so forgiving. I know what is progress raiding, what you need to offer, how you need to attend, how loot distribution works in different methods.
The game becomes a job, a duty, and you just wipe and wipe over weeks to beat content 5/7. That's why I don't play it. I have a job already that pays well enough, and after I'm done with it for the day, I don't want to continue it in-game. I want to have fun, relax my brain, turn off. Mythic raiding is the exact opposite.