I always figured that since Chrome = Google its primary purpose was to give Google complete information about its users' browsing habits, and hence that anyone who used it had given up on any meaningful definition of privacy.
However, Lightning isn't perfect. Out of the box it performs worse for tracking protection, using the EFF's test site, than Firefox (or even Edge!), and even customising its privacy settings it performs worse in some respects. That's not saying that others are better in all respects (Firefox's fingerprinting protection needs more work), but it's not a panacea. But my biggest reservation is that development on it seems to have stopped a few years ago, so there is no prospect of improvement.