Are you worried he's making your browser Catholic? I've met him, he's a great guy. Just because you might disagree with his political views doesn't mean you should choose your browser based on that difference.
I said a few years ago that Brave wasn't going anywhere, and it isn't. It's not because Brendan Eich donated to Prop 8 either. The vast majority of the large, liquid market of browser users simply don't care about privacy.
You don't seem to understand how Javascript actually works. It can do just about nothing on your computer. It can't read any data off disk (that the site itself didn't create). It can't read data from other websites, unless the website operator enabled that (in which case it could read that data with just URLs, no scripting required). It can't write data anywhere except into specific storage files. Besides HTTP requests, it can't access any other process, service or resource without asking you for permissions.
Telemetry is something that can be done without Javascript. I can just make any link you activate have some sort of unique ID. Maybe Javascript can make it a bit more detailed, but fundamentally nothing changes.