You know why Invoker is fun to play? Because he's a unique type of carry. What LoL lacks and what DotA has is many different viable types of carry.
There is PotM who carries on sheer utility. There are caster carries like Krob or Necrolyte who carry by outlasting the other team. Spectre, who carried by abusing the hell out of damage return. Necrolic who carried by essentially doing the opposite of what Spectre did. Tinker who carries by refreshing cooldowns on spells and items, Queen of Pain who carries on sheer mobility. Invoker is another one in the line of caries, and his way of carrying is unique too. When invoke is down to 5 second cooldown, it's really like playing Janna, except you also do damage. The allure of Invoker isn't that he's "complex", it's the fact that you can literally be a "caster carry". Late game, he actively carries with spells and he has a lot more tools at his disposal than the typical caster. There is actually something really cool about the concept of the Invoker, he's not just there to appease the hardcore players.
Also, I feel it's rather disingenuous to apply concepts like "anti-fun" and "burden of knowledge" to DotA. These concepts exist in LoL because Riot needs a framework for explaining the decisions they make as the developers of a game based on micro transactions. With someone as skilled at creating concepts as Zileas, I can definitely say that Riot succeeded in their goal. But these are not inspired by a desire to actually dig down to the truth of things. As such, they feel hollow compared to when Zileas outlined the concept of micromanagement back when Starcraft just came out. Honestly, I couldn't read past the part where Zileas was criticizing Kunkka's ult on "inefficient optimization". If a huge community favorite in DotA can be indicted under one or more of LoL's "design principles", then they aren't very good design principles.
Invoker makes perfect sense when you realize that the goal of DotA's developers was to serve the game rather than their bottom line. They didn't have to worry about the hero's accessibility or whether novice players would struggle to play against him. They just added something "cool" to the game. Now, I don't think there is anything wrong with caring primarily about the bottom line, but don't criticize other developers for not having the same goals as you.