I mean, look at the great online games of yesteryear - say, Quake for example. Quake's mechanics are fundamentally simple. Run, jump, pickup stuff, shoot. There's only 9ish weapons to figure out in the average Quake-like game, and in most cases the behavior is "point at what you want to die and click the button". Learn the maps so you can control the pickups. The hardcore players will have to learn to exploit the bugs in the motion model to get a little speed edge, but that basic stuff is all there.
And in a Deathmatch game, you know what happens if you suck? You die. Over and over and over and over again. But since it's a free-for-all, there's no teammates you're letting down. Nobody screaming at you about how much you suck. And even in a teamgame, the teams are larger so one weak player can fade in the back. And none of his teammates are watching him suck and screaming at him, they're all too busy playing and can't see what he's doing through walls. If he drops out, nobody cares.
But you can't say Quake et al are low-skill. See also RTS games - RTS team-games face many of the same problems as DOTAlikes, but in most RTSes the 1V1 matchups reign supreme, and FFA is also a popular option. In a 1V1 a newbie will get utterly annihilated repeatedly and there's the same bad slippery slope of DOTAlikes, but nobody will hate the loser like you'll see in a teamgame where everybody just watched one idiotic ally spend the last 25 minutes ruining their fun. Plus, RTS games at least will give you the dignity of a quick death unlike a DOTAlike where you'll still spend several minutes watching the towers go down before the victor is declared.
You could make a super-simple DOTA-like game with only one hero to choose from and super-simple combat mechanics and you'd still see all the cultural and mechanical problems you see in modern DOTAlikes. You'd still have players screaming at the newbie who's accidentally feeding. You'd still have players hurling verbal abuse at each other while they get pointlessly pummeled because the game is functionally over but doesn't have the dignity to end even though the leveling has made it completley moribund.
It's not about skill, it's about a long-form team-game with bad slippery slopes. A low-skill game with that format would still be cruel to newbies, just like high-skill games that avoid that insanity are newbie-friendly (see any twitch-FPS for example).
Games like that already exist and they don't capture any of the aspects of Dota I find compelling. The new Infinite Crisis game is essentially the Dominion game mode from League of Legends with DC superheroes and villains. There was another game like that announced recently for iOS with the slogan "No farming, just fighting." Those games all sound terrible to me. They're tailor-made for the attention-deficient iPhone gaming generation. Can the rest of us have a few games to play?
Quake was a great game but it's strategically and tactically shallow. Dota is an intrinsically team-based game with the tactical and strategical depth of a game like Starcraft. Arguably it surpasses Starcraft's depth in some areas owing to the many 5v5 match-ups you can generate from a pool of over 100 heroes. I disagree with nearly every adulteration Riot made in designing League of Legends, but even they realize that you cannot alter these features without making a different kind of game entirely.
Not every game has to be like chess where the rule set can be learned in five minutes.
Classic FPS's in minstagib mode are generally very simple to play with a total of about 3/4 controls and are very much skill, not trivia based, and an anathema to console gamers and noobs. Skill is not about memorizing dictionaries of trivia.
Anyway, key word is trivia.
The difference in skill between the ex-pro, or even several of the just very talented players and the rest of us is immense.
The trivia helps, knowing counter items and the like helps but at high level play all sorts of things become very important. For example positioning of your unit(s), to either miss a spell being cast or to physically block the person you are trying to kill makes the difference between a major win or complete loss of a fight. Or your ability to farm, last hitting creeps, stacking/jungling and maximizing your gold per second.
So yes at low level Dota is all about the trivia. I'm a better player then a random new player because I know the characters, their abilities and the items. But at the end of the day despite putting in hundreds of hours I pale in comparison to a Excellent player because I don't have the reflexes, or the split second analytical mind. In addition, and most importantly, I've not put in the hours upon hours of purposeful practice that a pro dota player has.
Dota is a skill based game.
There are built in user contributed guides that suggest what what to build and why, with the guide's author comments on both individual items and skills, for every hero and numerous alternative builds. There is in game voting on the quality of each guide. It's a cinch now in Dota 2 to buy basic stuff even if you've literally never played a hero before, and also easy to try experimental builds for fun right in game.
The skill is all judgement calls and spacing. Memorizing item or skill progressions is irrelevant and indeed "trivial" in the sense that it plays little part in the game or your thinking during it. On the other hand, having the skill to use the blink dagger and catch opponents or save yourself is essential.
Not to say that there isn't a fair share of unintuitive things. A good example is how even though the objective of the game is destroy the enemy base most of the times a team will avoid attacking the enemy buildings until the very end of the game.
You're saying that because obviously you haven't progressed past the trivia plateau.
There's a LOT of skill involved in DotA. You need a few hours of play to acquire the basic mechanics and principles of the game, but you need a lot more hours to become a good player - even if you already know your heroes and your builds. I've spent more than 1000 hours playing the original DotA (since 2004) and Heroes of Newerth, and I've seen a lot of mediocre players with a shitload of experience, as well as a lot of absolutely terrific players with only a few hours of play behind them.
Memorizing the basic knowledge required to play the game doesn't make you instantaneously a good player.
Besides, there is a great portion of skill in laning. You can watch best players like dendi winning 9 times of 10 on the middle lane against other top players. It's a spectacular feat.
League of Legends addresses many of your apparent concerns with Dota's game design. But guess what? Its online community is every bit as toxic and obnoxious. Both are skill-based team games that are played over the Internet, require a lot of coordination, and usually take over 30 minutes per match. You can address in-game bad manners at the margins with something like Riot's tribunal system or Valve's reporting system, but I doubt you can do much to eliminate the problem without also eliminating those essential features of their game design.