uBlock Origin is not so critical for a browser that comes with a decent ad blocker that is on by default.

If that were true then they wouldn't have committed to support v2 extensions past the sunset date in perpetuity (which they made a public announcement of) since uBO is the biggest reason for as indicated by other issues in their tracker as well as the fact that this ticket hasn't been immediately closed. Also, good luck with the privacy crowd if you're not providing feature-for-feature behavior in your native adblocker, which Brave's adblock does not.

You overlook how it is on by default yet it works well. Many browsers with security features inbuilt often visibly affect usability.