> This is doubly true for services like Google Search, and yet (for example) security-oriented engines like DDG are barely making a dent.

DDG is making a huge dent in the narrow segment it is designed to appeal to, which is all any specialized service can hope for. I think DDG fans persistently overestimate how many people find Google’s personalization a net cost.

> I honestly don't think niche is the way to go if you're trying to go after Google/YouTube/Facebook. You'd need to figure out a core issue or core need that has been overlooked.

Sure, if you are trying to replace one of those as the dominant mass market player in its domain you need to do that.

Also, I think you are more likely to find a core need by dealing with a need that seems niche but is really just more pronounced and visible in that particular niche than by digging around in the dark for a core need.