Well I could do so, but as said the majority won't really see the benefits of pushing so hard. They're willing to switch but not willing to advocate.
Slowly, by only replying in that group and sending my messages there, I was able to move more of them over and finally the other group died which lead to the last individuals to come over to Signal.
It takes time, but can be done.
Is it enough to stop using WhatsApp within one year?
Or should we be striving to migrate and delete our accounts before the policy change takes effect, to also prevent our historical WhatsApp data to be linked to our FB account?
I don't have a clear answer myself. Anyone more informed, please elaborate.