Don't know fedimint well. but my immediate reaction is it still a good thing to increase btc ownership. The reality of life is most people don't want to learn how to be fully non custodial, and self sovereign. most people will never make that effort. They just want to make a payment. they don't want to manage keys. Just like most people will never run their own email server, they will just use gmail. also making something with a good easy UI and making it decentralized and self custodial is mega hard, thus some form of centralisation