Let’s say I decide I’ve had enough with this whole Federation business and that humanity would be better represented by a Starfleet that follows my particular ideology. Assuming I could get enough people for crew and support, why can’t I start my own Starfleet?
I could replicate ship parts until I have a couple vessels. Go to new worlds and present myself as the official first contact of humanity. I could fly to Vulcan or Bajor and tell them no actually my organization represents humanity.
What’s going to stop me?
Controlled technology and not easily built from scratch even by Starfleet engineers.
The Relaunch novelverse expanded the concept and importance of industrial replicators. When Voyager returned to the Delta Quadrant, she led an small ‘Full Circle’ fleet that included a large engineering ship that did have industrial replicators large enough to reconstruct ships when severely damaged.
Lowere Decks and Prodigy have brought industrial replicators into onscreen canon.
Prodigy gave the Protostar prototype ship an industrial replicator large enough to construct shuttles. Lower Decks has shown the Cerritos and other ships tasked with delivering and bringing online very large industrial replicators on planets seeking Federation support.