That may seem like a plus from a user's perspective when websites were only tested with / optimized for Chrome. From the perspective of someone who's concerned about Google's power as a monopoly, alternative browsers being Chromium-based is just part of the problem. Sure, you can fork Chromium in theory, but making changes that are incompatible with Google's vision is going to be a problem for you. So Google is still going to be in control as long as they ship the browser that dominates all others. Brave don't have the resources to maintain an engine by themselves anyway. Besides Mozilla, only Apple and Microsoft could do it, and Microsoft already gave up.