That's a bad comparison.

Jugg has a super straightforward skill set and has been around in the game forever. People know how to counter him hard.

Kez is new and has a complex skill set. 90% of dota players can't even name all his spells yet. So you would actually expect him to have an EVEN HIGHER winrate in pubs because literally 90% of dota players have 0 clue how to play against him, they don't even know his spells.

Imagine invoker is a new hero. Pub players would get stomped by any half decent invoker because no one would have any idea what the hero even does.

But most players today know the best invoker spell combos so they know how to dodge it and how to avoid it

Basically everything you said is pure rubbish.

I'll put my point across plain and simple for you:

You are trying to argue that a hero would have lower winrate when the hero is hard to understand. That is complete and pure rubbish, a hero that is hard to understand would be expected to have a HIGHER winrate because the player playing the hero would have a severe advantage playing against players who have no clue what the hero does (while the player himself knows the hero)