Whether it be an individual or an organization, living a “life” centered around fundamental principles is a never-ending effort. For Mozilla, I suppose those principles are, in theory, the Mozilla Manifesto.
I don’t claim to be an expert on Mozilla, especially on the thinking that goes on internally (since much of that strategy is developed “behind the scenes”). But I do know what changes I have observed over the last 19 years, and I do listen to smart people who also have their own opinions. And the refrain I hear a to a troubling extent goes along the lines of “Mozilla has lost its way”. 
Now, I don’t think any organization or person should stay static, but if either is truly driven by governing principles, and those principles have face validity, then there should be some consistency in the general approaches and activities one undertakes year after year.
For many years now, I’ve been a fan of the author Stephen Covey, who thought and wrote quite a bit about principle-centered living. A few of his thoughts from his book “Principle-Centered Leadership” could be applied to the Mozilla that I (and others?) perceive over the past several years (emphasis added):
My experience tells me that people instinctively trust those whose personality is founded upon correct principles. We have evidence of this in our long-term relationships.
To value oneself and, at the same time, subordinate oneself to higher purposes and principles is the paradoxical essence of highest humanity and the foundation of effective leadership.
Correct principles are like compasses: they are always pointing the way. And if we know how to read them, we won’t get lost, confused, or fooled by conflicting voices and values.
Principles are self-evident, self-validating natural laws.
The lesson of history is that to the degree people and civilizations have operated in harmony with correct principles, they have prospered. At the root of societal declines are foolish practices that represent violations of correct principles.
Principles, unlike values, are objective and external.
Values are like maps. Maps are not the territories; they are only subjective attempts to describe or represent the territory.
When people align their personal values with correct principles, they are liberated from old perceptions or paradigms.
So like @giannisk, I also worry about selection & use of proprietary tools, as such choices do prima facie seem to contradict the principles expressed in the Manifesto. And I don’t think we’re the only ones that notice that cognitive dissonance.
I do feel (hope?) that I’m pragmatic enough that it’s important to not let strict interpretation to values hold you back from “getting work done”, so when there are not software options that reasonably get the job done, I totally understand falling back to a proprietary offering. But on the other hand, one should consider whether or not they have the capacity to support the open source ecosystem to bring “sub-par” tools up to the standards one needs.
(Big props to the team that has done that with Discourse, for example. Not only has Discourse been able to better meet the needs of the Mozilla community, but these improvements have helped other Discourse users too. The open source world needs more of that, and stuff the the MOSS grants are super valuable!)
So anyway, I don’t think there is an easy answer here. But in any org I’ve worked with or been a part of, I’ve always pushed folks to constantly remember & reflect on their guiding principles, and try to always keep their work “in check” to either align with those principles, or if necessary, adjust those principles to reflect the current reality of the organization. Maybe more of that principle-driven thoughtfulness within & throughout Mozilla would help to change what negative perceptions are out there. It may not be the only way, but certainly couldn’t hurt. 