Many modern day "Evangelical" Protestants consider Romans 14:5 as the chief proof text for the notion there can be "non-essential" doctrines within Christianity. While there are practices throughout Christian history that can be considered "non-essentials," it is more problematic to apply this to the category of "doctrine," since doctrine implies essential teaching. The logic that certain Protestants use typically reduces down to making almost nothing an "essential" and thus stripping Christianity of anything solid that gives it shape. But when read carefully, we see here that Paul was speaking in a relatively narrow range of 'liberty' in Christian disciplines, especially as these were tied to one's former life and thus they had a certain sensitivity to them, not merely a personal preference. In fact, Paul refers to these people who need special care as those who are "weak in faith," but didn't mean it as an insult, just that they were not mature enough to thrive, which all Christians are called to aspire to.
Let's look at the passage of Chapter 14 of Romans:
1 As for the one who is weak in faith, welcome him, but not to quarrel over opinions [Greek: "scruples" / "doubts"]. 2 One person believes he may eat anything, while the weak person eats only vegetables. 3 Let not the one who eats despise the one who abstains, and let not the one who abstains pass judgment on the one who eats, for God has welcomed him. 4 Who are you to pass judgment on the servant of another? It is before his own master that he stands or falls. And he will be upheld, for the Lord is able to make him stand. 5 One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. 6 The one who observes the day, observes it in honor of the Lord. The one who eats, eats in honor of the Lord, since he gives thanks to God, while the one who abstains, abstains in honor of the Lord and gives thanks to God. 7 For none of us lives to himself, and none of us dies to himself. 8 For if we live, we live to the Lord, and if we die, we die to the Lord. So then, whether we live or whether we die, we are the Lord's. ... 13 Therefore let us not pass judgment on one another any longer, but rather decide never to put a stumbling block or hindrance in the way of a brother. 14 I know and am persuaded in the Lord Jesus that nothing is unclean in itself, but it is unclean for anyone who thinks it unclean. 15 For if your brother is grieved by what you eat, you are no longer walking in love. By what you eat, do not destroy the one for whom Christ died.
The verse "one person esteems one day better than another" is commonly taken to mean that when it comes to the day of worship, that is a "non-essential" doctrine, and that it is really the freedom of each individual Christian to decide whether they want to worship alone or with a community, or on Sunday or on Saturday, etc. With this mindset, these Protestants "conclude" that a true Christian could just sleep in on Sunday and not have to worship in any formal sense at all. These Protestants claim that 14:5 proves that the Church, clergy, etc, cannot even set rules/standards such as how to worship, nor set rules on fasting, etc. But was Paul really giving each Christian such "liberty"? Only a surface level and non-contextual reading could lead to such an "interpretation," while careful look at Paul's language will see he's speaking very carefully and pastorally.
