Mozilla has had several "PR nightmare" decisions that a vocal set of users didn't like, and sometimes were genuinely ill advised/bad/shitty. But as far as I can see they do not have a bad track record when it comes to security/privacy. Do you have any examples of actual serious security/privacy fuck ups by Mozilla/Firefox? I mean that stood up to scrutiny beyond the sensationalist headlines?
Their defaults might not be your defaults, but they are even working on bringing Tor into mainstream Firefox. None of this means they are above criticism of course, but... context!
The sum total of their actions points towards an organisation that has some internal problems but that is genuinely pursuing privacy and an open web as a goal for as many users as possible.