Personally I don't get overly excited about the tracking/re-targeting, but what did bother me was how ridiculously intrusive the ads on some sites that totally destroyed my user experience, wasted my batteries and cellular data and at times prevented me from (on mobile) from getting to the content I actually wanted.
With mobile it was also the stupid number of accidental clicks when scrolling, or pop ups with really small 'x' to close that and a non-zoomable viewport.
Wasting my time (and somebody else's money) on ads I never wanted to click does't seem like a good or sustainable economic value add.
Sometimes ads can be useful. On Google search sometimes the people who will pay for ads are sometimes a better signal than those that SEO their way to the top. Similarly I have discovered things of interest in Facebook & Twitter ads where they were relevant to me.
It does seem that online advertising is in need of a bit of a 'reboot'.