Well, you just described the definition of adware--your defense of it is that it's easy-to-ignore adware?
If that's where Internet advertising settles, then I might actually be OK with that. And there's plenty that I'm a long way from OK with.
I've had numerous performance and memory issues with Firefox but from my testing over the years it's the closest to Chrome/Chromium you can get.
Also Firefox gets new features fairly regularly. It's still an "innovative" browser, as opposed to Chromium which is mostly stagnant. Vertical tabs are pretty cool.
Personally, I just got to like Firefox over time.
It is more true to my ideals.