Google and other companies make it extremely convenient and easy, so you don't need to be technically inclined to use their services and everyone already uses them. Asking someone to join the Fediverse requires them to understand what it is, and deal with the learning curve; if they aren't technically inclined, they are almost certain to refuse, and even many technically capable ones don't care enough.

Signal is a much better compromise; private enough that it isn't creepy to use, and easy enough that anyone who uses WhatsApp can pick up without difficulty or friction. Even then, only a small percentage of the people in my life use it. It is what it is.

You can't force people to care. The vast majority of people never even heard of FOSS, never heard of self-hosting (or even know what hosting is), and don't get me started on the Fediverse... Most people don't care about privacy either; my mother for example is the "if you have nothing to hide, you have nothing to fear" type.

When you say "they refuse to take part", it puts too much blame on people, you can't expect people to do something that they don't understand or care enough about. It's like if I asked you to come with me to protest against something you've never heard of, but in order to understand what's wrong with it, you need a long lecture and actually pay attention. Corporations spent hundreds of billions on making their services and products really convenient and easy, so they have to screw up really badly to get people to switch.