Comment by nabakin
They're trying to diversify their revenue so it doesn't all come from Google. All these 'self-indulgent projects' are attempts to actually make enough money to compete with a multi-trillion dollar company's resources because they know they can't compete long-term.
The parent is referring to things like Coop (social media), SkyWriter (IDE), Persona, Solo (website builder), “data futures”, Servo [1], “big blue button”, most of them have little to no potential for revenue.
Meanwhile you can’t really have more than a few YouTube tabs open in FF otherwise it starts freezing, and it’s been behind Safari in adding new features for a while.
[1] including Servo here since it seems to have had no real roadmap to become integrated into FF, making it more of a vanity project - it’s already thirteen years old at this point