Passing tests and has abysmal performance on basic web features. Not to mention how many security issues are present. Its unserious to suggest it as an alternative at this stage. It make people think they dont have to support firefox because there is alternatives just around the corner.

How much does Firefox pass? 99.99%?

the acid test is surfing the web. it doesn't matter how many tests it passes if users can't get to the sites they want and use them the way they want because their browser doesn't support some feature properly or because gets rejected by the sites for not being Chrome/Safari/Firefox.