One of the problems is that Firefox is often compared with soft-fork browsers.
Mozilla needs to develop the whole browser. They have to pay hundreds of devs. For that, they do need search engine deals and ad placements and all that.
That also means, they have to retain mainstream appeal, so they will ship features that some idealists may not like, like the recent AI features.
That's where virtually all criticism comes from, that Mozilla needs to make money to continue developing the browser.
And that even though all this stuff is easy to disable. Firefox forks like LibreWolf are cool, because they offer a configuration preset you can point people to.
What's not cool, is that lots of folks consider it a moral failing of Mozilla, that they don't ship LibreWolf's defaults. If they did, there would be no Firefox anymore and no LibreWolf.

