That's just it, though. Doctrine isn't just something we come up with off the cuff. Doctrine has a source - the Word of God. Rome claims that its traditions are on par with Scripture, but (amusingly) does so on the basis that Scripture says so in II Thessalonians 2:15 (which it doesn't of course, the "traditions" Paul mentions were orally preached analogs to the written truths appearing in his epistles). However, no professing church has any authority apart from the Word of God - The Bible defines what "the church" even is. The Word of God is what gives churches their authority to teach and preach and conduct matters internally within their own membership - not "tradition" (which can mean anything, and HAS meant just about anything over the past 1600 years of Catholicism). The measure of whether a professing Christian is doctrinally correct or not correct has nothing to do with whether they agree or disagree with some denomination or group. It is measured by how their theology stacks up against the Bible as it is systematically exegeted.
Which is to claim for the individual what is collectively claimed by many denominations. But not, it seems, the Episcopal Church or the Presbyterian Church USA, who seem to have dumped Scripture as a standard.