Most users will only use an ad blocker that is built-in. You should consider how elitist it is to confine ad blockers to users who know and trust certain extensions vetted by their community, but not the remaining extensions which have been a minefield.
Having a built-in ad blocker doesn't hinder an app from also accepting extensions which block ads.
Originally I wasn't even concerned about an adblocker being built-in. I
was just afraid that it will be used as an argument against more
powerful extensions.
But you brought up another point: I think it is in the nature of an
adblocker, that it MUST be "elitist" to be actually useful. If every
browser does "adblocking" by default, the ads will just adapt. That
will be as useless as the HTTP-Header "dont-track-me".
Good, let ads adapt. Then the adblockers adapt once more. And so on, and so forth. If ads were delivered by the same source/domain (ie. it wasn't outsoured to an ad network who also do profiling) people would have less issues with them.
Not wanting my workflow broken and replaced with inferior software is "elitist"? I don't think so. I hope your attitude isn't prevalent inside of Mozilla. You can say that breaking existing extensions isn't necessary, yet that's exactly what has already happened once and seems like it will happen again.
Yeah, a lot of it is elitist. In other parts of this thread people are complaining about Vimperator being broken by the switch to WebExtensions.
The switch to WebExtensions allowed all the excellent performance improvements we have been seeing in Firefox over the last year. So it improved the performance for everyone, and broke a feature that a small minority used. That minority is a highly specialized, highly trained, bunch.
If you think that features that benefit a small elite group of users should trump improvements for all, then I think that is an elitist attitude.
Also, here there is absolutely no talk about changing extension APIs. So I don't see why extensions that work now shouldn't continue working in FF Preview once Extension support is added. The situation is pretty unlike the WebExtension situation.
So yeah, hold their feet to the fire to make sure that things don't regress without need. But also look at what they are trying to do with merging the FF Focus stuff in, and getting a built-in adblocker. They are doubling down on privacy for all. This should be commended.
People are not less deserving of stable software or good UX by virtue of being highly specialized and highly trained. These users, as much as anybody, have every right to be upset when their software experience is degraded, so I reject your premise unequivocally. If opinions like yours are prevalent inside Mozilla, then the organization has gone cancerous and I fear it's days of producing praise-worthy software are drawing to a close.
Consider the following: over the years I have convinced a dozen or two users in non-technical careers to switch to firefox. Most of them do not install extensions, at least for themselves. However, without extensions, I would not have recommended firefox to them in the first place. Firefox's rise in popularity is owed to the word of mouth campaign carried out primarily by people with technical/foss careers or inclinations. Why would I, or anybody, suggest a browser that I do not enjoy using? To suggest software to somebody is to go out on a limb for that software, because if the person you are suggesting it to has a bad experience with that software, your personal reputation will take the hit for recommending it. So why on earth would I stick my neck out to promote Firefox when Firefox is no longer software that cares about the needs of users like myself? If Firefox has adopted a "socially progressive" model of disregarding the needs of technical users because such users have more software-privilege, then they have taken the wind out of their own sails[sales].
(I put the words 'social progress' in scare-quotes because I also reject the premise that infantilizing software is in fact socially progressive. In truth it's socially regressive, since it's effectively technical people deliberately reducing the exposure non-technical users have to technical problems that might challenge them to learn more. The true impact of infantilizing consumer software is to pull the ladder up behind us. Reinforcing and widening the dichotomy between technical and non-technical users is inherently socially regressive.)
Extensions can be a good thing for sure. But they need to be done right. Hacking out some hurried implementation of extensions is how malware and security advisories happen. It is elitist to suggest that the desires of the 3% trump building a good browser first.
Also, the Internet and most technology happens to break existing workflows. We shouldn't assume disruption is bad if the result is an improved version.
Having a built-in ad blocker doesn't hinder an app from also accepting extensions which block ads.