After all, we talk about a game where you have over 100 champions with completely different skill sets, over 100 in-game items to buy, all creating a huge array of possible plays and counterplays... That at the same time requires split-second reflexes, maintaining map awareness and, the hardest part, good teamwork.
Actually my main problem with LoL is that you have to spend money to access champions. In DotA I'm used to having access to a huge complement of heroes, and a common strategy is choosing heroes specifically because they are powerful against the enemy team (counter-picking). In LoL it's a lot harder since you only have like 20 (or fewer?) heroes available.
Paying for champions is paying for additional content -- content that's free in DotA 2.
No you don't because of Influence points. Playing games acquires you IP which you can use to buy champions. All champions can be bought with IP
Runes on the other hand, do allow for slight advantages during a game. They're also free (as in, you can't even buy them with real money), but once you've gathered an amount of in game currency (Influence Points), you have to choose between using those IP to buy runes or champions. So while everything that's able to give you an advantage in the game is free, those investing real money will have a wider range of champions and/or runes sooner.
The biggest different between Dota 2 and LoL is pricing model.
Dota 2 is free. Really free. You have access to 100+ heroes from your first game and there isn't a single thing you can buy that has an effect on winning or losing a match. It's all skins, alternate announcers, and other stuff just for fun.
LoL is free... to play. There are a set of heroes that are free at any given time which is constantly rotating. You have to pay to unlock heroes permanently or can unlock them very slowly over time. You will never unlock everyone without paying money. There are additional other systems you have to level up, or can pay to level more quickly, that provide small bonuses to character attributes in game.
This effects more than the price.
For example in Dota 2 one of my favorite modes is "Reverse Draft" where each team picks the OTHER team's heroes. So you try and give your opponent the worst team you can think of. Something like this is impossible in LoL because every person only has access to a small set of heroes.