thompson
They will still create a profile of you even when you delete your stuff. Not for undelete like Reddit does, but for completing the whole picture of who people are and why they say and do what they do. And that requires data from other platforms, small and large.
In the digital world we live in now it's more about not giving them personal info they really shouldn't have. The rest can be "easily" found with money and promise of influence/power. So beware of the innocent and highly useful apps with multiyear excellent userfeedback that are supposed to charge you money each month, then suddenly goes free and hidden in settings shows they are selling "ads" to Facebook, although no ads were ever shown. Makes sense that the app tries to tell you to always be recording sound for best performance.
With enough money you don't need direct sourcing. There are so many who are willing to do it for you for pennies, while you are used to shell out billions just for keeping the CEO out of court/deposition.
My advice to you is to try live a normal life. Just limit sharing personal info to those who don't need it. If you don't want ANY info be available about you then go watch some Alaska/Canada mountainmen shows. Few want to live like that. Meaning if you want to have a "normal" life you need to give up some info. Just try limit exactly what.
As others have mentioned; that's where GrapheneOS comes into the picture. User profiles, split tunneling VPN and remove all app permissions they don't actually need will give you a jumpstart.