These exist. But so long as adivertisers can buy ads with tracking, fraud detection etc, they will.

The key to getting reasonable ads back is making the bad ads impossible for advertisers to buy.

Also, curious to see how an ad network can guarantee that its creatives don’t misbehave, this is brand safety played on “godlike” (sorry for bad Unreal reference).

Do you have a reference? Looking around I didn't see anything. I might have missed it though.

Maybe Carbon ads?

Yeah, carbon seems to be pretty good. I used to see it on codepen and some other design website. Always relevant, but carbon seems limited to developers and designers.

Some other ad thing which doesn't need tracking: Sponsored posts or targeting people who follow someone on Instagram.

Yes, carbon is probably the biggest one.

Do you think any ad purchaser will actually buy such an ad? What would be the engagement rates of such ads be?

I am not sure how viable such a company will be in the real world.

One big problem is that ad fraud is rampant. Knowing a person is really seeing the ad is very important, which tracking helps you confirm to a certain degree.