I think this is naive, and the overall comment is equally ideological as you're accusing mozilla as being.
Advertiser-funded social networks will always have incentives that are misaligned with users. They want to optimise for impressions so they can drive more views. It's been demonstrated so often that social networks optimise for engagement bait - putting content that drives hate clicks in timelines - to juice engagment numbers and get more ad views.
Decentralised and ad-free are distinct qualities of a social network, but they do work hand-in-hand to produce a pro-user network. It is harder for a decentralised modal to make an anti-user change because everyone else can work against them - we saw this to an extent with third party twitter accounts not having the algorithmic timeline.