I'm scared to say that Safari comes closest but you're just in Apple's walled garden then instead of someone elses'.
Our only hope seems to lie with Ladybird, if that even ends up being good and it seems extensions aren't on the agenda at least for a while.
If the vast majority of endusers want to live in the moat, I can't stop them, but at least I'd like an alternative to explore interesting content even if my bank, etc will never support it.
At least banks are regulated enough that I don't expect their websites to be running full-page video ads anytime soon.
I told our dev teams to not even bother testing because, on our b2b site, Firefox usage was under 0.01%. That is not a typo. I can't spend dev time on that.
They're doing the same, and now playing VC, an industry at which they have no apparent expertise.
Every browser alternatives you can reasonably choose today is going to be either Blink (Chromium-based) or Gecko (Firefox-based). And then you have WebKit (Safari).
Ladybird, Flow and Dillo are really the only true alternative browsers in active development other than a few others running on niche operating systems (to which I'm throwing in all of the DOS browsers...).