It's not about retards being retards - it's about giving incentives to retards for being retards. I never expect anything from your regular pub player, but having a carrot dangling on a stick as a side goal is a detriment to the simple objective of winning the game, plain and simple. I'm sorry if you can't understand this simple concept. I'm saying that the game is objectively worse when people have other things in mind than winning; that's not to say that everyone has winning in mind all the time, but having sidegoals incentivized and sanctioned is a bad thing.
That is something that almost exclusively happens in lower brackets though, at least I haven't seen a single stupid itemchoice on a hero that doesn't fit the bill (yet, it will inevitably happen obviously) thanks to quests. I do however see a lot of retarded item decision every single day on almost every core. The amount of games I lost because people didn't get a bkb instead of whatever shitty luxury item they got instead probably amounts to 30-40% of the losses. Same goes for the opponent obviously, so in the end it evens out when it comes to the winratio. Same goes for people losing games because they did a stupid challenge, and since you don't do it you have a 4/9 chance that the retard is on your side, 5/9 that he's on the opponents side so your MMR should increase even more!
I do agree that having these quests around may influence people to do stuff they otherwise wouldn't, but as I mentioned earlier Valve doesn't really care for the solo-player experience. It's basically a tradeoff between not having this stuff in game at all, disabling quests to be doable in ranked games or doing it the way it is now. I personally prefer number 3.
Second, I'm not blaming items for the bad quality of play - that's a strawman argument and entirely your construction. I do think it's amusing that you're saying everyone knows 100% of the juke paths on the map, and that being able to see them clearly through an item does not constitute a definitive advantage. I certainly don't know all the juke paths and in the heat of the moment it's especially hard to have clarity, and I have played over 6000 hours of Dota 2.
You misunderstood me, I'm not saying everyone knows them but everyone who actually cares about winning does (or rather: should) because it's just one of the easier things to learn. So what exactly is the problem with the new terrain then? Either you already know all this stuff and it doesn't impact you, or you can use the terrain and improve your knowledge of the game. These juke-paths exist on the normal map though so people complaining about not being able to utilize the new terrain to "improve" is just them being lazy. When they introduce new juke-spots I start up a lobby and test them out, takes 5 minutes of my time every major patch (so basically every 4 months). I would imagine a lot of people that complain about the new terrain being "pay to win" would be too lazy to do the same, and yet they argue that their opponents have an advantage thanks to the terrain?
I do think most Dota players are shit and even my real life friends who I play with are shit, that's not a problem. It's incentivizing shitty play that's the issue.
I partly agree. There will always be incentives for people to do stuff they otherwise wouldn't. A new immortal for techies had them in basically every other game for the first week or so, which was a time I decided not to even start up dota since I couldn't stomach it. A new amazing item for some random hero saw them have a rise in pickrate even when the hero itself was shit all around or simply didn't fit the draft and yet people lastpicked them. While they're certainly less "in your face" like the quest system, I do think that drawing a line somewhere in between would upset a lot of people either way and is thus hard to accomplish.
I do feel like Valve could've drastically improved the quest system by disabling it in the new seasonal ranked mode, which would open up a whole new group of complainants that feel that they need to pay to not have quests in their game but would enable a very win-oriented type of queue, and removing item-based quests entirely. Quests like "stun for x amounts of seconds", "get roshan before minute x", "gank x people in their own jungle" etc. are pretty great because unless you want to spam the quest 10 times before eventually finishing it you have to think about which heroes/drafts can accomplish these goals efficiently, thus improving your overall game knowledge. Just yesterday I had three different friends of mine ask what hero I'd suggest for a couple of these challenges because they could only think of the most obvious ones.