You’re confusing difficulty of the game with skill level of opponents
How many maps does HOTS have? What about the competition? If you’re learning it is much easier to learn 1 thing than many
What about micro? DOTA and LoL are low micro games because you can insta-die
Macro? In LoL you go to lanes and farm then you go mid and fight over dragon/baron. Whoever has teleport clears out the sidelanes. In HOTS minion control is paramount because you are getting gold (xp) for your whole team/denying it for their whole team