I think you're expecting it to solve a problem it's not intended to solve.

I'm not expecting it to block all javascript, or all malicious javascript. I'm just expecting it to block most or all of the annoying stuff on the web.

To the extent that this is the job it's being hired for, you don't really need to 'trust' it. You run it and it either does what you want or it doesn't. Personally it suits my needs perfectly.