The ONLY reason why its harder to get into dota 2 than is because there are no "noob games" for people to learn harder things in somewhat relaxed conditions, instead they are thrown into matchmaking with the likes of you who expect from them impossible tasks and throw a hissyfit every time they dont do something properly. They dont NEED to learn harder things from the get go, they however absolutely NEED to get a good feel of the game pace and need to get comfortable playing the game and heroes and against heroes/combos without being called noob every two minutes.
The game needs to get tutorials asap for sure, but the mentor program and game going live free for everyone are the more important things. I went with friend who has played like 2 hours of LoL before, he picked easy hero and was stomped nontheless, because even after i warned him dozen times, he still dived enemy tower against dazzle yurnero. But he was HAVING FUN... Until two wannabe-pros started flaming him.
The issue arent the newbies or the knowledge they have or dont have. Its those seasoned players that cant get over few missteps of those newbies that might cost them the game.
I havent played quake like at all, since it was just not my thing, I always preferred CS, but again, the only reason SC2 is easier to get into is because you get matched against opponents on your level of (no)skill, this just isnt possible in dota2 at this time with the regular matchmaking and the ammount of people that (can) play. If half of their matches were against low masters, you can bet new people wouldnt play SC2 for more than few games, too.