Reddit is like a distillation of that, the logical end point of it ... if that is a dead end, Google is in for a rough time with the pathway they are pursuing with Chrome.
And by "never worked very well," I don't just mean "We ran ads without good results." The whole experience was just sort of confusing and underwhelming, especially when compared to other channels like FB or Google. We suspected that the majority of our clicks were bots, based on our own analytics. The targeting always felt unreliable. Support interactions were weird. In general, the platform always just felt kind of... janky.
Don't know if that's still the case now, but at least as of a year or so ago, I knew a lot of people working in digital marketing who felt the same about the platform.