I agree with those statements if you're just a consumer. However, if you're some sort of content creator, the story is slightly different: your audience might be still solely on the platforms you're trying to avoid.
Example: I'm a hobbyist photographer; I have like maybe 1000 people following me in total across Facebook and Instagram. I signed up for Pixelfed a few days ago; haven't explored much yet, but I'd be surprised if I see even one person I know there. Even if I start posting on Pixelfed exclusively, my photos will probably still end up on Facebook and Instagram, possibly with zero credit. Maybe if I start posting to Pixelfed in parallel and slowly move away from Meta, I don't know...