You are going on the premise that wizards are still trying to make themselves completely invisible to the muggle world. It's a possibility, even after a major magical sighting, wizards cold still keep themselves fully invisible and totally removed from muggles.

I was considering the situation where the two societies interact. So wizards would not be walking around wearing notice-me-not charms (if they were forced to consistently use them, it's damned easy to see how they would get pissed off). Muggles would know where the wizards live and could harass them there.

Wizards might be able to apparate away (not everyone can - read cannon, apparating is difficult, and fires connected to the floo network are not available on the streets) and they may be able to disillusion themselves (again the average wizard is not capable of this) but the very fact that they had to would be enough to piss them off.

Muggle repelling wards work on building not people, to a person walking down the street a muggle repelling ward is useless. They could use it on their houses, but then again, those only work if the muggles do not know that the building is there and expressly want to go there.

In short while dumb hypotheses are dumb, you're assumptions that all wizards are highly skilled is far dumber, as are you in general.

 

Actually, most wizards can apparate: it's the equivalent of having a driving license in the wizarding world.

What we're told in GoF is that many wizards don't like to apparate.

Er... why would such a situation come about?

Also, it's not like wizards have a huge sign over their heads announcing them to be wizards. If they wear Muggle clothes, they look like a Muggle. You don't really need notice-me-not charms, invisibility or apparation.

(Also note that your claim that disillusionment is an rare skill is not backed up by the books. Though our heroes don't use it, there are many things that "fully qualified adult wizards" can do that our heroes cannot apparently by virtue of having left Hogwarts - obviously an attempt by JKR to limit the powers of our heroes. Note how previous generations were much better at magic.)