The charter of the NT church is found in the NT ..no where is there authority to add doctrine , or to change Gods revelation to the Jews.. The NT churches were functioning independently only loosely joined by the doctrine that had been preached to them ...
Of course, some have to see the early Church looking like the cornucopia of beliefs in “independent” churches today.
St. Paul would have none of that. Both Holy Scripture and history testify against it.
Whatever you or another see as doctrine, the canon, whatever, it really all comes down to authority.
Either Christ established His Church with a hierarchy and authority as we see in Holy Scripture and continuing throughout history thereafter; or, He left it up to each individual’s authority - which we do not see in Scripture or anywhere in Christianity - until modern times.