Also how are they performing ad blocking? Are they just shipping it with u-block origin or their own technology?
Not to put anyone down, but I don't think people realise how hard it is to deliver a secure and working web browser. They are basically OS scale.
Only one "purchasing" decision to make at that point.
It was trustworthy, until it wasn't.
These things don't make them inherently evil, the world isn't black and white and people doing good still need money, but it flips your idea about singularizing trust in the browser maker on it's head.
I would prefer a world where all browsers have integrated ad blocking, in which case I only have to make a decision on browser, not browser + ad blocking extension.
Firefox itself already has some features to protect your privacy. Why go through the trouble of creating a whole new browser where a combination of tweaks in settings and maybe a plugin for FF would yield similar results?
Seeking out a different browser to use takes similar, if not greater effort than just installing uBlock Origin (or a similar extension, or a few) and possibly altering some browser settings.
Plus, there's the issue of trust - how many people can vouch for a particular browser, or an extension? If a malicious piece of code would get into a niche browser or extension, how long would it take for someone to notice and bring that to the attention of the wider community? Would there even be such a community? Or maybe if they'd sell out and the product would change ownership?
The more eyes there are looking at code and how it runs, the safer it is, or at least i'd argue so. Therefore, sticking with the popular options is probably better, in general. In this case, that would probably (hopefully) be Firefox with some addons.