> There is some level of centralization if I want to buy a domain name or do other certain things, but it's pretty minimal and I feel mostly in control, at least for the kind of things I want to do.

This actually related to a fundamental lack of control.

Lots of tech we buy now promises "smart" but because you need to get to it from your phone, some corporation "needs" to "help" connect your device and your phone.

for example - you want a "smart" thermostat. To connect to it from anywhere from your phone to change the temperature, the thermostat contacts the mannufacturer. Then your phone has to talk to them as an intermediary to contact your thermostat.

Conveniently, they can collect data from your thermostat, or your house, or your phone, maintain a "customer relationship" or even charge you for the "service".

if things were properly decentralized, your phone could just contact your "smart" stuff and nobody else would need to be involved.